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The current carbon dioxide (CO 2 ) evolution-based standard method for determining biodegradable microplastics (MPs) degradation neglects its priming effect on soil organic matter decomposition, which misestimates their biodegradability. Here, a 13 C natural abundance method was used to estimate the mineralization of poly(lactic acid) (PLA) MP in various agricultural soils, and to trace its utilization in different microbial groups. In alkaline soils, the PLA-derived CO 2 emissions increased with increasing soil carbon/nitrogen (C/N) ratios, and the mineralization of PLA MP concentrations ranged from 3-33 %, whereas the CO 2 evolution method probably over- or under-estimated the mineralization of PLA in alkaline soils with different soil C/N ratios. Low PLA mineralization (1-5 %) were found in the acidic soil, and the standard method largely overestimated the mineralization of PLA MP by 1.3- to 3.3-fold. Moreover, the hydrolysate of PLA MP was preferentially assimilated by Gram-negative bacteria, but Gram-positive bacterial decomposition mainly contributed to the release of PLA-derived CO 2 at low MP concentrations (≤ 1 %). Overall, the 13 C natural abundance method appears to be suitable for tracking the mineralization and microbial utilization of biodegradable PLA in soils, and the PLA-derived C is mainly assimilated and decomposed by bacterial groups., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

C 2 photosynthesis is a photosynthetic pathway in which photorespiratory CO 2 release and refixation are enhanced in leaf bundle sheath (BS) tissues. The evolution of C 2 photosynthesis has been hypothesized to be a major step in the origin of C 4 photosynthesis, highlighting the importance of studying C 2 evolution. In this study, physiological, anatomical, ultrastructural, and immunohistochemical properties of leaf photosynthetic tissues were investigated in six non-C 4 Tribulus species and four C 4 Tribulus species. At 42°C, T. cristatus exhibited a photosynthetic CO 2 compensation point in the absence of respiration (C * ) of 21 µmol mol -1 , below the C 3 mean C * of 73 µmol mol -1 . Tribulus astrocarpus had a C * value at 42°C of 55 µmol mol -1 , intermediate between the C 3 species and the C 2 T. cristatus. Glycine decarboxylase (GDC) allocation to BS tissues was associated with lower C * . Tribulus cristatus and T. astrocarpus allocated 86% and 30% of their GDC to the BS tissues, respectively, well above the C 3 mean of 11%. Tribulus astrocarpus thus exhibits a weaker C 2 (termed sub-C 2 ) phenotype. Increased allocation of mitochondria to the BS and decreased length-to-width ratios of BS cells, were present in non-C 4 species, indicating a potential role in C 2 and C 4 evolution., (© 2024 The Author(s). Plant, Cell & Environment published by John Wiley & Sons Ltd.)

Biomethanation represents a promising approach for biomethane production, with biofilm-based processes like trickle bed reactors (TBRs) being among the most efficient solutions. However, maintaining stable performance can be challenging, and both pure and mixed culture approaches have been applied to address this. In this study, inocula enriched with hydrogenotrophic methanogens were introduced to to TBRs as bioaugmentation strategy to assess their impacts on the process performance and microbial community dynamics. Metagenomic analysis revealed a metagenome-assembled genome belonging to the hydrogenotrophic genus Methanobacterium, which became dominant during enrichment and successfully colonized the TBR biofilm after bioaugmentation. The TBRs achieved a biogas production with > 96 % methane. The bioaugmented reactor consumed additional H 2. This may be due to microbial species utilizing CO 2 and H 2 via various CO 2 reduction pathways. Overall, implementing bioaugmentation in TBRs showed potential for establishing targeted species, although challenges remain in managing H 2 consumption and optimizing microbial interactions., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Author(s). Published by Elsevier Ltd.. All rights reserved.)

Microalgae biotechnology holds great potential for mitigating CO 2 emissions, yet faces challenges in commercialization due to suboptimal photosynthetic efficiency. This study presents an innovative approach to improve CO 2 mass transfer efficiency in microalgae using carbonic anhydrase (CA) in an internal LED flexible air-lift photobioreactor. Optimal conditions initial inoculation with 3.55 × 10 6 cells/mL and 20 % CO 2 concentration, complemented by white LED lighting in Chlorella sp. CA regulated intracellular composition, enhancing chlorophyll, lipid, and protein contents. Metabolomics revealed elevated malic and succinic acids, associated with increased Ribulose 1,5-bisphosphate carboxylase oxygenase (RuBisCO) and Acetoacetyl coenzyme A (Acetyl-CoA) activities, facilitating efficient carbon fixation. CA also mitigated cellular oxidative stress by reducing reactive oxygen species (ROS). Furthermore, CA improved extracellular electron acceptor with currents surpassed CK. This CA-based microalgae biotechnology provides a foundation for future commercial applications, addressing CO 2 emissions., Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Yun Liu reports financial support was provided by Science and Technology Innovation Special Foundation for Carbon Peak and Carbon Neutrality of Jiangsu Province. Yun Liu reports financial support was provided by National Natural Science Foundation of China. Liu, Y., Yao, D.D., Wu, L.Y., Tan, D., K. Tian., Zhang Y. has patent The invention relates to an airlift photobioreactor with built-in LED light source for microalgae culture issued to Yun Liu. If there are other authors, they declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Accumulations of macroalgal wrack are important for adequate functioning of the beach ecosystem. However, the sudden beaching of seaweed masses smothers the coastline and forms decomposing piles on the shore, harming tourism-based economies, but also affecting the beach ecosystem metabolism. The decomposition of sudden pulses of wrack can modify the biogeochemistry of beach sands and increase greenhouse gas (GHG) emissions. The presence of invasive species in the wrack deposits can superimpose harmful effects on the beach functioning. We quantified the wrack biomass of Rugulopteryx okamurae, an invasive species of extreme impact, on five sandy beaches from the Atlantic coast of the Strait of Gibraltar (Spain), and we tested the effects on in situ respiratory CO 2 fluxes using an infrared gas analyser. All the beaches showed massive accumulations of Rugulopteryx wrack deposits. However, the biomass changed significantly between beaches, ranging (mean ± SE) from 968.3 ± 287.7 kg m -1 to 9210 ± 1279.4 kg m -1 of wet weight. Wrack supported high respiration rates, with CO 2 fluxes averaging (±SE) 19.15 ± 5.5 μmol CO 2 m -2 s -1 across beaches, reaching astounding maximum peaks of 291 μmol CO 2 m -2  s -1 . The within-beach variability was related to the distance of the wrack deposits from the shoreline, as the average metabolic rates tended to increase significantly from the swash to the drift line. Thicker wrack and a more degraded algae stage showed significantly higher CO 2 fluxes. We estimated that the annual CO 2 flux of R. okamurae in our study area ranged between 0.39 (±0.01) and 23.30 (±11.33) kg C m -2 y -1 . We suggest that massive amounts of beach wrack can become a globally significant contributor to GHG emissions that can offset any potential carbon-sink capacity of macroalgal forests. However, the piles of wrack located several meters above the drift line showed non-measurable CO 2 efflux. Transferring beach wrack from swash to drier upper-beach areas, a common practice in many coastal regions suffering from massive wrack accumulations, might help reduce GHG emissions while removing the wrack stockpiles from the intertidal. However, this practice is not necessarily suitable for all beaches and can create ecological and conservation problems in the dune system. There is an urgent need to implement practical and sustainable management practices for massive wrack deposits capable of presenting various solutions to achieve a balance between conservation and recreation actions, answering the consequences of a problem that links both, environmental and economic issues., Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: IFR reports financial support was provided by Government of Andalusia. IFR reports financial support was provided by Spain Ministry of Science and Innovation. IFR reports financial support was provided by European Social Fund. IG reports financial support was provided by Government of Spain Ministry of Universities. ABI reports was provided by European Maritime and Fisheries Fund. IFR reports equipment, drugs, or supplies was provided by European Regional Development Fund. If there are other authors, they declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Authors. Published by Elsevier Ltd.. All rights reserved.)

CO 2 -based poly(3-hydroxybutyrate) (PHB) can be produced by the versatile bacterium Cupriavidus necator through chemolithoautotrophic fermentation, using a gas mixture consisting of CO 2 , H 2 , and O 2 . Despite offering a propitious route for carbon-neutral bioplastic manufacturing, its adoption is currently hampered by the wide explosive range of the required gas mixture, as well as the limited gas-to-liquid mass transfer rates. To address these challenges, pressure fermentation was applied as a robust and effective strategy, while ensuring safe operation by adhering to the limiting O 2 concentration, utilizing state-of-the-art bioreactors. Consequently, exponential growth could be prolonged, boosting CO 2 -based PHB production from 10.8 g/L at 1.5 bar up to 29.6 g/L at 3 bar. The production gain closely aligns with the theoretical calculations, except for when the pressure was increased up to 4 bar. Overall, the demonstrated increase in PHB production underscores the potential of pressure fermentation to enhance aerobic gas fermentation., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024. Published by Elsevier Ltd.)

Utilizing carbon dioxide (CO 2 ) for valuable chemical production is key to a circular economy. Current processes are costly due to limited microorganism use, low-value products, and the need for affordable energy. This study addresses these challenges by using industrial contaminants like thiosulfate (S 2 O 3 2- ) for CO 2 conversion into ectoines. Ectoines, are important ingredients as pharmaceuticals and cosmetics. Here, six microbial genomes were identified as potential candidates to valorize CO 2 and S 2 O 3 2- into ectoine. After laboratory validation at 3 % NaCl, the fastest-growing strain, Guyparkeria halophila, was optimized at 6 %, 9 %, and 15 % NaCl, showing the highest specific ectoine contents (mg Ect  g biomass -1 ) at 15 %. Batch bioreactors, combining optimal conditions, achieved maximum specific ectoine contents of 47 %. These results not only constitute the highest ectoine content so far reported by autotrophs and most of heterotrophs, but also the first proof of a novel valorization platform for CO 2 and S 2 O 3 2- , focused on pharmaceuticals production., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Author(s). Published by Elsevier Ltd.. All rights reserved.)

The superior productivity of C 4 plants is achieved via a metabolic C 4 cycle which acts as a CO 2 pump across mesophyll and bundle sheath (BS) cells and requires an additional input of energy in the form of ATP. The importance of chloroplast NADH dehydrogenase-like complex (NDH) operating cyclic electron flow (CEF) around Photosystem I (PSI) for C 4 photosynthesis has been shown in reverse genetics studies but the contribution of CEF and NDH to cell-level electron fluxes remained unknown. We have created gene-edited Setaria viridis with null ndhO alleles lacking functional NDH and developed methods for quantification of electron flow through NDH in BS and mesophyll cells. We show that CEF accounts for 84% of electrons reducing PSI in BS cells and most of those electrons are delivered through NDH while the contribution of the complex to electron transport in mesophyll cells is minimal. A decreased leaf CO 2 assimilation rate and growth of plants lacking NDH cannot be rescued by supplying additional CO 2 . Our results indicate that NDH-mediated CEF is the primary electron transport route in BS chloroplasts highlighting the essential role of NDH in generating ATP required for CO 2 fixation by the C 3 cycle in BS cells., (© 2024 The Author(s). New Phytologist © 2024 New Phytologist Foundation.)

The response of mesophyll conductance (g m ) to CO 2 plays a key role in photosynthesis and ecosystem carbon cycles under climate change. Despite numerous studies, there is still debate about how g m responds to short-term CO 2 variations. Here we used multiple methods and looked at the relationship between stomatal conductance to CO 2 (g sc ) and g m to address this aspect. We measured chlorophyll fluorescence parameters and online carbon isotope discrimination (Δ) at different CO 2 mole fractions in sunflower (Helianthus annuus L.), cowpea (Vigna unguiculata L.), and wheat (Triticum aestivum L.) leaves. The variable J and Δ based methods showed that g m decreased with an increase in CO 2 mole fraction, and so did stomatal conductance. There were linear relationships between g m and g sc across CO 2 mole fractions. g m obtained from A-C i curve fitting method was higher than that from the variable J method and was not representative of g m under the growth CO 2 concentration. g m could be estimated by empirical models analogous to the Ball-Berry model and the USO model for stomatal conductance. Our results suggest that g m and g sc respond in a coordinated manner to short-term variations in CO 2 , providing new insight into the role of g m in photosynthesis modelling., (© 2024 John Wiley & Sons Ltd.)

Heatwaves, expected to become more frequent, pose a significant threat to plant biomass production. This experiment was designed to estimate heatwave influence on Brassica juncea phytoremediation when superimposed on different CO 2 levels. A 7-day heatwave was generated during the species flowering stage. Heatwaves decreased all B. juncea dry weights. The lowest species dry weight was recorded when the heatwave was accompanied by 250 ppm CO 2 , in which the biomass significantly decreased by 40.0% relative to that of no heatwave under the same atmospheric CO 2 conditions. Heatwave superposition with 250 ppm CO 2 reduced the Cd content in B. juncea aerial parts by 28.1% relative to that of identical environmental conditions without heatwave, whereas the opposite result was observed under 550 ppm CO 2 conditions. The heatwave caused oxidative damage to B. juncea under all CO 2 conditions, as manifested by increased malondialdehyde levels in the plant shoots. With heatwave superposition, antioxidant enzyme activity was enhanced by exposure to 400 and 550 ppm CO 2 . Considering biomass yield generation and Cd uptake capacity, heatwave superposition decreased the B. juncea phytoremediation effects, and high atmospheric CO 2 conditions could alleviate detrimental effects to a certain extent. This study uniquely examines the combined effects of heatwaves and varying CO 2 levels on phytoremediation, providing microscopic insights into oxidative damage and enzyme activity, highlighting the potential for CO 2 enrichment to mitigate heatwave impacts, and offering comprehensive analysis for future agricultural practices and environmental management., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

In recirculating aquaculture systems (RAS), waste management of nutrient-rich byproducts accounts for 30-50% of the whole production costs. Integrating microalgae into RAS offers complementary solutions for transforming waste streams into valuable co-products. This review aims to provide an overview of recent advances in microalgae application to enhance RAS performance and derive value from all waste streams by using RAS effluents as microalgal nutrient sources. Aquaculture solid waste can be converted by hydrothermal liquefaction (HTL), then the resultant aqueous phase of HTL can be used for microalgae cultivation. In addition, microalgae generate the required oxygen while sequestering carbon dioxide. The review suggests a novel integrated system focusing on oxygenation and carbon dioxide capture along with recent technological developments concerning efficient microalgae cultivation and nutrient recovery techniques. In such system, microalgae-based biorefineries provide environmentally-conscious and economically-viable pathways for enhanced RAS performance and conversion of effluents into high-value products., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Author(s). Published by Elsevier Ltd.. All rights reserved.)

Carbon supplementation strategies still have certain practical application constraints. Zn/Fe-based metal-organic frameworks (MOFs) nanoparticles that which are not toxic to Scenedesmus obliquus were successfully introduced into microalgal solutions to overcome low CO 2 solubility. The maximum specific surface area of MOFs reached 342.94 m 2 ·g -1 at a Zn/Fe molar ratio of 10/1. Under the optimal MOFs concentrations of 2.5 mg·L -1 , the conversion of inorganic carbon increased by 2.6-fold. When S. obliquuswas cultured in a MOFs-modified medium with 1.50 % CO 2 at 25 °C, the CO 2 mass transfer coefficient and mixing time reached 9.01 × 10 -3 min -1 and 55 s, respectively. The maximum chlorophyll-a content, biomass productivity, and CO 2 fixation efficiency reached 32.57 mg·L -1 , 0.240 g·L -1 ·d -1 and 21.6 %, respectively. Enriching CO 2 for ribulose-1,5-bisphosphate carboxylase/oxygenase carboxylation by MOFs may be the key to improving the photosynthetic efficiency of microalgae. This strategy could serve as a reference for improving the microalgal CO 2 fixation efficiency., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024. Published by Elsevier Ltd.)

Aim: How the cerebral metabolic rates of oxygen and glucose utilization (CMRO 2 and CMR Glc , respectively) are affected by alterations in arterial PCO 2 (PaCO 2 ) is equivocal and therefore was the primary question of this study., Methods: This retrospective analysis involved pooled data from four separate studies, involving 41 healthy adults (35 males/6 females). Participants completed stepwise steady-state alterations in PaCO 2 ranging between 30 and 60 mmHg. The CMRO 2 and CMR Glc were assessed via the Fick approach (CBF × arterial-internal jugular venous difference of oxygen or glucose content, respectively) utilizing duplex ultrasound of the internal carotid artery and vertebral artery to calculate cerebral blood flow (CBF)., Results: The CMRO 2 was altered by 0.5 mL × min -1 (95% CI: -0.6 to -0.3) per mmHg change in PaCO 2 (p < 0.001) which corresponded to a 9.8% (95% CI: -13.2 to -6.5) change in CMRO 2 with a 9 mmHg change in PaCO 2 (inclusive of hypo- and hypercapnia). The CMR Glc was reduced by 7.7% (95% CI: -15.4 to -0.08, p = 0.045; i.e., reduction in net glucose uptake) and the oxidative glucose index (ratio of oxygen to glucose uptake) was reduced by 5.6% (95% CI: -11.2 to 0.06, p = 0.049) with a + 9 mmHg increase in PaCO 2 ., Conclusion: Collectively, the CMRO 2 is altered by approximately 1% per mmHg change in PaCO 2 . Further, glucose is incompletely oxidized during hypercapnia, indicating reductions in CMRO 2 are either met by compensatory increases in nonoxidative glucose metabolism or explained by a reduction in total energy production., (© 2024 The Author(s). Acta Physiologica published by John Wiley & Sons Ltd on behalf of Scandinavian Physiological Society.)

A short period of exposure to elevated CO 2 is known to decrease evapotranspiration via stomatal closure. Based on theoretical evaluation of a canopy transpiration model, we hypothesized that this decrease in the evapotranspiration of rice under elevated CO 2 was greater under higher temperature conditions due to an increased sensitivity of transpiration to changes in CO 2 induced by the greater vapour pressure deficit. In a temperature gradient chamber-based experiment, a 200 ppm increase in CO 2 concentration led to 0.4 mm (-7%) and 1.5 mm (-15%) decreases in 12 h evapotranspiration under ambient temperature and high temperature (+3.7°C) conditions, respectively. Model simulations revealed that the greater vapour pressure deficit under higher temperature conditions explained the variations in the reduction of evapotranspiration observed under elevated CO 2 levels between the temperature treatments. Our study suggests the utility of a simple modelling framework for mechanistic understanding of evapotranspiration and crop energy balance system under changing environmental conditions., (© 2024 John Wiley & Sons Ltd.)

Understanding the short-term responses of mesophyll conductance (g m ) and stomatal conductance (g sc ) to environmental changes remains a challenging yet central aspect of plant physiology. This review synthesises our current knowledge of these short-term responses, which underpin CO 2 diffusion within leaves. Recent methodological advances in measuring g m using online isotopic discrimination and chlorophyll fluorescence have improved our confidence in detecting short-term g m responses, but results need to be carefully evaluated. Environmental factors like vapour pressure deficit and CO 2 concentration indirectly impact g m through g sc changes, highlighting some of the complex interactions between the two parameters. Evidence suggests that short-term responses of g m are not, or at least not fully, mechanistically linked to changes in g sc , cautioning against using g sc as a reliable proxy for g m . The overarching challenge lies in unravelling the mechanistic basis of short-term g m responses, which will contribute to the development of accurate models bridging laboratory insights with broader ecological implications. Addressing these gaps in understanding is crucial for refining predictions of g m behaviour under changing environmental conditions., (© 2024 The Authors. Plant, Cell & Environment published by John Wiley & Sons Ltd.)

Mesophyll conductance (g m ) is a crucial plant trait that can significantly limit photosynthesis. Measurement of photosynthetic C 18 O 16 O discrimination (Δ 18 O) has proved to be the only viable means of resolving g m in both C 3 and C 4 plants. However, the currently available methods to exploit Δ 18 O for g m estimation are error prone due to their inadequacy in constraining the degree of oxygen isotope exchange (θ) during mesophyll CO 2 hydration. Here, we capitalized on experimental manipulation of leaf water isotopic dynamics to establish a novel, nonsteady state, regression-based approach for simultaneous determination of g m and θ from online Δ 18 O measurements. We demonstrated the methodological and theoretical robustness of this new Δ 18 O-g m estimation approach and showed through measurements on several C 3 and C 4 species that this approach can serve as a benchmark method against which to identify previously-unrecognized biases of the existing Δ 18 O-g m methods. Our results highlight the unique value of this nonsteady state-based approach for contributing to ongoing efforts toward quantitative understanding of mesophyll conductance for crop yield improvement and carbon cycle modeling., (© 2024 The Author(s). New Phytologist © 2024 New Phytologist Foundation.)

The growing demand for global food production is likely to be a defining issue facing humanity over the next 50 years. To tackle this challenge, there is a desire to bioengineer crops with higher photosynthetic efficiencies, to increase yields. Recently, there has been a growing interest in engineering leaves with higher mesophyll conductance (g m ), which would allow CO 2 to move more efficiently from the substomatal cavities to the chloroplast stroma. However, if crop yield gains are to be realised through this approach, it is essential that the methodological limitations associated with estimating g m are fully appreciated. In this review, we summarise these limitations, and outline the uncertainties and assumptions that can affect the final estimation of g m . Furthermore, we critically assess the predicted quantitative effect that elevating g m will have on assimilation rates in crop species. We highlight the need for more theoretical modelling to determine whether altering g m is truly a viable route to improve crop performance. Finally, we offer suggestions to guide future research on g m , which will help mitigate the uncertainty inherently associated with estimating this parameter., (© 2024 The Authors. Plant, Cell & Environment published by John Wiley & Sons Ltd.)

C 4 NAD-malic enzyme (NAD-ME) species occurs in drier regions and exhibit different drought responses compared to C 4 NADP-malic enzyme (NADP-ME) species. However, a physiological mechanism explaining the geographical discrepancies remains uncertain. This study examined gas exchange patterns that might explain different distributions observed between two subtypes of C 4 photosynthesis. We measured the response of leaf gas exchange to vapour pressure deficit (VPD) and CO 2 in plants from six distinct C 4 clades having closely related NAD-ME and NADP-ME species using a Li-Cor 6400 gas exchange system. We found that NAD-ME species exhibited greater relative reductions in stomatal conductance with increases in VPD than NADP-ME species but observed no consistent subtype differences in C 4 cycle activity as indicated by the initial slope of the A response to intercellular CO 2 concentration. Based on these results, we hypothesise the greater response of g s to increasing VPD may enable NAD-ME plants to outperform NADP-ME plants in hot, dry environments where VPD is normally high., (© 2024 The Authors. Plant, Cell & Environment published by John Wiley & Sons Ltd.)

Cultivating cells in shake flasks is a routine operation that is largely unchanged since its inception. A glass or plastic Erlenmeyer vessel with the primary gas exchange taking place across various porous plugs is used with media volumes typically ranging from 100 mL to 2 L. Oxygen limitation and carbon dioxide accumulation in the vessel is a major concern for studies involving shake flask cultures. In this study, we enhance mass transfer in a conventional shake flask by replacing the body wall with a permeable membrane. Naturally occurring concentration gradient across the permeable membrane walls facilitates the movement of oxygen and carbon dioxide between the flask and the external environment. The modified flask called the breathable flask, has shown a 40% improvement in mass transfer coefficient (k L a) determined using the static diffusion method. The prokaryotic cell culture studies performed with Escherichia coli showed an improvement of 28%-66% in biomass and 41%-56% in recombinant product yield. The eukaryotic cell culture study performed with Pichia pastoris expressing proinsulin exhibited a 40% improvement in biomass and 115% improvement in protein yield. The study demonstrates a novel approach to addressing the mass transfer limitations in conventional shake flask cultures. The proposed flask amplifies its value by providing a membrane-diffusion-based sensing platform for the integration of low-cost, noninvasive sensing capabilities for real-time monitoring of critical cell culture parameters like dissolved oxygen and dissolved carbon dioxide., (© 2024 Wiley Periodicals LLC.)

Automated measurements of the ratio of concentrations of methane and carbon dioxide, [CH 4 ]:[CO 2 ], in breath from individual animals (the so-called "sniffer technique") and estimated CO 2 production can be used to estimate CH 4 production, provided that CO 2 production can be reliably calculated. This would allow CH 4 production from individual cows to be estimated in large cohorts of cows, whereby ranking of cows according to their CH 4 production might become possible and their values could be used for breeding of low CH 4 -emitting animals. Estimates of CO 2 production are typically based on predictions of heat production, which can be calculated from body weight (BW), energy-corrected milk yield, and days of pregnancy. The objectives of the present study were to develop predictions of CO 2 production directly from milk production, dietary, and animal variables, and furthermore to develop different models to be used for different scenarios, depending on available data. An international dataset with 2,244 records from individual lactating cows including CO 2 production and associated traits, as dry matter intake (DMI), diet composition, BW, milk production and composition, days in milk, and days pregnant, was compiled to constitute the training dataset. Research location and experiment nested within research location were included as random intercepts. The method of CO 2 production measurement (respiration chamber [RC] or GreenFeed [GF]) was confounded with research location, and therefore excluded from the model. In total, 3 models were developed based on the current training dataset: model 1 ("best model"), where all significant traits were included; model 2 ("on-farm model"), where DMI was excluded; and model 3 ("reduced on-farm model"), where both DMI and BW were excluded. Evaluation on test dat sets with either RC data (n = 103), GF data without additives (n = 478), or GF data only including observations where nitrate, 3-nitrooxypropanol (3-NOP), or a combination of nitrate and 3-NOP were fed to the cows (GF+: n = 295), showed good precision of the 3 models, illustrated by low slope bias both in absolute values (-0.22 to 0.097) and in percentage (0.049 to 4.89) of mean square error (MSE). However, the mean bias (MB) indicated systematic overprediction and underprediction of CO 2 production when the models were evaluated on the GF and the RC test datasets, respectively. To address this bias, the 3 models were evaluated on a modified test dataset, where the CO 2 production (g/d) was adjusted by subtracting (where measurements were obtained by RC) or adding absolute MB (where measurements were obtained by GF) from evaluation of the specific model on RC, GF, and GF+ test datasets. With this modification, the absolute values of MB and MB as percentage of MSE became negligible. In conclusion, the 3 models were precise in predicting CO 2 production from lactating dairy cows., (The Authors. Published by Elsevier Inc. on behalf of the American Dairy Science Association®. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).)

Mesophyll conductance (g m ) describes the ease with which CO 2 passes from the sub-stomatal cavities of the leaf to the primary carboxylase of photosynthesis, Rubisco. Increasing g m is suggested as a means to engineer increases in photosynthesis by increasing [CO 2 ] at Rubisco, inhibiting oxygenation and accelerating carboxylation. Here, tobacco was transgenically up-regulated with Arabidopsis Cotton Golgi-related 3 (CGR3), a gene controlling methylesterification of pectin, as a strategy to increase CO 2 diffusion across the cell wall and thereby increase g m . Across three independent events in tobacco strongly expressing AtCGR3, mesophyll cell wall thickness was decreased by 7%-13%, wall porosity increased by 75% and g m measured by carbon isotope discrimination increased by 28%. Importantly, field-grown plants showed an average 8% increase in leaf photosynthetic CO 2 uptake. Up-regulating CGR3 provides a new strategy for increasing g m in dicotyledonous crops, leading to higher CO 2 assimilation and a potential means to sustainable crop yield improvement., (© 2024 The Authors. Plant Biotechnology Journal published by Society for Experimental Biology and The Association of Applied Biologists and John Wiley & Sons Ltd.)

Introduction: Carbon dioxide-dependent Proteus mirabilis has been isolated from clinical specimens. It is not clear whether mutations in carbonic anhydrase are responsible for the carbon dioxide dependence of P. mirabilis. The pathogenicity of carbon dioxide-dependent P. mirabilis also remains unclear. The purpose of this study was to determine the cause carbon dioxide dependence of P. mirabilis and its pathogenicity., Methods: The DNA sequence of can encoding carbonic anhydrase of a carbon dioxide-dependent P. mirabilis small colony variant (SCV) isolate was analyzed. To confirm that impaired carbonic anhydrase activity is responsible for the formation of the carbon dioxide-dependent SCV phenotype of P. mirabilis, we performed complementation experiments using plasmids with intact can. Additionally, mouse infection experiments were performed to confirm the change in virulence due to the mutation of carbonic anhydrase., Results: We found that the can gene of the carbon dioxide-dependent P. mirabilis SCV isolate showed had a frameshift mutation with a deletion of 1 bp (c. 173delC). The can of P. mirabilis encodes carbonic anhydrase was also found to function in Escherichia coli. The cause of the carbon dioxide-dependent SCV phenotype of P. mirabilis was an abnormality in carbonic anhydrase. Nevertheless, no changes were observed in virulence due to the mutation of carbonic anhydrase in mouse infection experiments., Conclusions: The can gene is essential for the growth of P. mirabilis in ambient air. The mechanisms underlying this fitness advantage in terms of infection warrant further investigation., Competing Interests: Declaration of competing interest The authors declare that there are no conflicts of interest., (Copyright © 2024 Japanese Society of Chemotherapy, Japanese Association for Infectious Diseases, and Japanese Society for Infection Prevention and Control. Published by Elsevier Ltd. All rights reserved.)

Photorespiration is an essential process related to photosynthesis that is initiated following the oxygenation reaction catalyzed by rubisco, the initial enzyme of the Calvin-Benson-Bassham cycle. This reaction produces an inhibitory intermediate that is recycled back into the Calvin-Benson-Bassham cycle by photorespiration which requires the use of energy and the release of a portion of the carbon as CO 2 . The energy use and CO 2 release of canonical photorespiration form a foundation for biochemical models used to describe and predict leaf carbon exchange and energy use (ATP and NAPDH). The ATP and NADPH demand of canonical photorespiration is thought to be different than that of the Calvin-Benson-Bassham cycle, requiring increased flexibility in the ratio of ATP and NADPH from the light reactions. Photorespiration requires many reactions across the chloroplasts, mitochondria and peroxisomes and involves many intermediates. Growing evidence indicates that these intermediates do not all stay in photorespiration as typically assumed and instead feed into other aspects of metabolism and leave as glycine, serine, and methylene-THF. Here we discuss how alternative flux through and from canonical photorespiration alters the ATP and NADPH requirements of metabolism following rubisco oxygenation using additional derivations of biochemical models of leaf photosynthesis and energetics. Using these new derivations, we determine that the ATP and NADPH demands of photorespiration are highly sensitive to alternative flux in ways that fundamentally changes how photorespiration contributes to the ratio of total ATP and NADPH demand. Specifically, alternative flows of carbon through photorespiration could reduce ATP and NADPH demand ratio to values below what is produced from linear electron transport., (© 2024 The Author(s). Plant, Cell & Environment published by John Wiley & Sons Ltd.)

Background: Biological control of insect pests is encountering an unprecedented challenge in agricultural systems due to the ongoing rise in carbon dioxide (CO 2 ) level. The use of entomopathogenic fungi (EPF) in these systems is gaining increased attention, and EPF as crop endophytes hold the potential for combining insect pest control and yield enhancement of crops, but the effects of increased CO 2 concentration on this interaction are poorly understood. Here, the introduction of endophytic EPF was explored as an alternative sustainable management strategy benefiting crops under elevated CO 2 , using maize (Zea mays), Asian corn borer (Ostrinia furnacalis), and EPF (Beauveria bassiana) to test changes in damage to maize plants from O. furnacalis, and the nutritional status (content of carbon, nitrogen, phosphorus, potassium), biomass, and yield of maize., Results: The results showed that endophytic B. bassiana could alleviate the damage caused by O. furnacalis larvae for maize plants under ambient CO 2 concentration, and this effect was enhanced under higher CO 2 concentration. Inoculation with B. bassiana effectively counteracted the adverse impact of elevated CO 2 on maize plants by preserving the nitrogen content at its baseline level (comparable with ambient CO 2 conditions without B. bassiana). Both simultaneous effects could explain the improvement of biomass and yield of maize under B. bassiana inoculation and elevated CO 2 ., Conclusion: This finding provides key information about the multifaceted benefits of B. bassiana as a maize endophyte. Our results highlight the promising potential of incorporating EPF as endophytes into integrated pest management strategies, particularly under elevated CO 2 concentrations. © 2024 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry., (© 2024 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.)

Gas exchange measurements enable mechanistic insights into the processes that underpin carbon and water fluxes in plant leaves which in turn inform understanding of related processes at a range of scales from individual cells to entire ecosytems. Given the importance of photosynthesis for the global climate discussion it is important to (a) foster a basic understanding of the fundamental principles underpinning the experimental methods used by the broad community, and (b) ensure best practice and correct data interpretation within the research community. In this review, we outline the biochemical and biophysical parameters of photosynthesis that can be investigated with gas exchange measurements and we provide step-by-step guidance on how to reliably measure them. We advise on best practices for using gas exchange equipment and highlight potential pitfalls in experimental design and data interpretation. The Supporting Information contains exemplary data sets, experimental protocols and data-modelling routines. This review is a community effort to equip both the experimental researcher and the data modeller with a solid understanding of the theoretical basis of gas-exchange measurements, the rationale behind different experimental protocols and the approaches to data interpretation., (© 2024 The Authors. Plant, Cell & Environment published by John Wiley & Sons Ltd.)

The conversion of carbon dioxide (CO 2 ) to methane (CH 4 ) is a strategy for sequestering CO 2 . Zero-valent iron (ZVI) has been proposed as an alternative electron donor for the CO 2 reduction to CH 4 . In this study, the effects of ZVI concentrations on the abiotic production of H 2 (without the action of microorganisms) in the first part and on the biological conversion of CO 2 to CH 4 using ZVI as a direct electron donor in the second part were examined. In the abiotic H 2 production, the increase in the ZVI concentration from 16 to 32, 64, and 96 g/L was found to have positive effects on both the amounts of H 2 generated and the rates of H 2 production because the extent of ZVI oxidation positively correlates with increasing surface area. Nevertheless, the increase in ZVI concentration from 96 to 224 g/L did not benefit the H 2 production because the ZVI dissolution was suppressed by the increasing aqueous pH above 10. In the bioconversion of CO 2 to CH 4 using ZVI as an electron donor, the main methanogenesis pathway occurred via hydrogenotrophic methanogenesis at pH 8.7-9.5 driven by the genus Methanobacterium of the class Methanobacteria. At ZVI concentrations of 64 g/L and above, the production of volatile fatty acid (VFA) became clear. Acetate was the main VFA, indicating the induction of homoacetogenesis at ZVI concentrations of 64 g/L and above. In addition, the presence of propionate as the second major VFA suggests the production of propionate from CO 2 and acetate under conditions with high H 2 partial pressure. The results indicated that the pathway for ZVI/CO 2 conversion to CH 4 was competitive between hydrogenotrophic methanogenesis and homoacetogenesis., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024. Published by Elsevier Inc.)

Despite their acidic pH, carbonated beverages can be contaminated by spoilage microorganisms. Thermal treatments, before and/or after carbonation, are usually applied to prevent the growth of these microorganisms. However, the impact of CO 2 on the heat resistance of spoilage microorganisms has never been studied. A better understanding of the combined impact of CO 2 and pH on the heat resistance of spoilage microorganisms commonly found in carbonated beverages might allow to optimize thermal treatment. Five microorganisms were selected for this study: Alicyclobacillus acidoterrestris (spores), Aspergillus niger (spores), Byssochlamys fulva (spores), Saccharomyces cerevisiae (vegetative cells), and Zygosaccharomyces parabailii (vegetative cells). A method was developed to assess the impact of heat treatments in carbonated media on microbial resistance. The heat resistances of the five studied species are coherent with the literature, when data were available. However, neither the dissolved CO 2 concentration (from 0 to 7 g/L), nor the pH (from 2.8 to 4.1) have an impact on the heat resistance of the selected microorganisms, except for As. niger, for which the presence of dissolved CO 2 reduced the heat resistance. This study improved our knowledge about the heat resistance of some spoilage microorganisms in presence of CO 2 ., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. none, (Copyright © 2024 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Utilizing CO 2 for bio-succinic acid production is an attractive approach to achieve carbon capture and recycling (CCR) with simultaneous production of a useful platform chemical. Actinobacillus succinogenes and Basfia succiniciproducens were selected and investigated as microbial catalysts. Firstly, the type and concentration of inorganic carbon concentration and glucose concentration were evaluated. 6 g C/L MgCO 3 and 24 g C/L glucose were found to be the optimal basic operational conditions, with succinic acid production and carbon yield of over 30 g/L and over 40%, respectively. Then, for maximum gaseous CO 2 fixation, carbonate was replaced with CO 2 at different ratios. The "less carbonate more CO 2 " condition of the inorganic carbon source was set as carbonate: CO 2 = 1:9 (based on the mass of carbon). This condition presented the highest availability of CO 2 by well-balanced chemical reaction equilibrium and phase equilibrium, showing the best performance with regarding CO 2 fixation (about 15 mg C/(L·hr)), with suppressed lactic acid accumulation. According to key enzymes analysis, the ratio of phosphoenolpyruvate carboxykinase to lactic dehydrogenase was enhanced at high ratios of gaseous CO 2 , which could promote glucose conversion through the succinic acid path. To further increase gaseous CO 2 fixation and succinic acid production and selectivity, stepwise CO 2 addition was evaluated. 50%-65% increase in inorganic carbon utilization was obtained coupled with 20%-30% increase in succinic acid selectivity. This was due to the promotion of the succinic acid branch of the glucose metabolism, while suppressing the pyruvate branch, along with the inhibition on the conversion from glucose to lactic acid., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023. Published by Elsevier B.V.)

The construction and optimization of microbial cell factories are crucial steps and key technologies in achieving green biomanufacturing. As concern has been aroused regarding the excessive carbon dioxide (CO 2 ) emissions and food security, a new and promising research field, microbial conversion of CO 2 into food compounds, has emerged. The research in this field not only holds significant implications for achieving the carbon peaking and carbon neutrality goals but also plays a role in maintaining food security. This paper provides a comprehensive review and outlook of the research on utilizing CO 2 and its derived low-carbon chemicals for the production of food compounds, focusing on the production of glucose, sugar derivatives, and single-cell proteins and the development of artificial CO 2 fixation pathways.

Background and Aims: The benefits and costs of amphistomy (AS) vs. hypostomy (HS) are not fully understood. Here, we quantify benefits of access of CO2 through stomata on the upper (adaxial) leaf surface, using 13C abundance in the adaxial and abaxial epicuticular wax. Additionally, a relationship between the distribution of stomata and epicuticular wax on the opposite leaf sides is studied., Methods: We suggest that the 13C content of long-chain aliphatic compounds of cuticular wax records the leaf internal CO2 concentration in chloroplasts adjacent to the adaxial and abaxial epidermes. This unique property stems from: (1) wax synthesis being located exclusively in epidermal cells; and (2) ongoing wax renewal over the whole leaf lifespan. Compound-specific and bulk wax 13C abundance (δ) was related to amphistomy level (ASL; as a fraction of adaxial in all stomata) of four AS and five HS species grown under various levels of irradiance. The isotopic polarity of epicuticular wax, i.e. the difference in abaxial and adaxial δ (δab - δad), was used to calculate the leaf dorsiventral CO2 gradient. Leaf-side-specific epicuticular wax deposition (amphiwaxy level) was estimated and related to ASL., Key Results: In HS species, the CO2 concentration in the adaxial epidermis was lower than in the abaxial one, independently of light conditions. In AS leaves grown in high-light and low-light conditions, the isotopic polarity and CO2 gradient varied in parallel with ASL. The AS leaves grown in high-light conditions increased ASL compared with low light, and δab - δad approached near-zero values. Changes in ASL occurred concomitantly with changes in amphiwaxy level., Conclusions: Leaf wax isotopic polarity is a newly identified leaf trait, distinguishing between hypo- and amphistomatous species and indicating that increased ASL in sun-exposed AS leaves reduces the CO2 gradient across the leaf mesophyll. Stomata and epicuticular wax deposition follow similar leaf-side patterning., (© The Author(s) 2024. Published by Oxford University Press on behalf of the Annals of Botany Company.)

Leaves experience near-constant light fluctuations daily. Past studies have identified many limiting factors of slow photosynthetic induction when leaves transition from low light to high light. However, the contribution of photorespiration in influencing photosynthesis during transient light conditions is largely unknown. This study employs dynamic measurements of gas exchange and metabolic responses to examine the contribution of photorespiration in constraining net rates of carbon assimilation during light induction. This work indicates that photorespiratory glycine accumulation during the early light induction contributes 5-7% to the additional carbon fixed relative to the low light conditions. Mutants with large glycine pools under photorespiratory conditions (5-formyl THF cycloligase and hydroxypyruvate reductase 1) showed a transient spike in net CO 2 assimilation during light induction, with glycine buildup accounting for 22-36% of the extra carbon assimilated. Interestingly, levels of many C 3 cycle intermediates remained relatively constant in both mutants and wild-type throughout the light induction period where glycine accumulated, indicating that recycling of carbon into the C 3 cycle via photorespiration is not needed to maintain C3 cycle activity under transient conditions. Furthermore, our data show that oxygen transient experiments can be used as a proxy to identify the photorespiratory component of light-induced photosynthetic changes., (© 2024. The Author(s).)

ConspectusLife is an exergonic chemical reaction. The same was true when the very first cells emerged at life's origin. In order to live, all cells need a source of carbon, energy, and electrons to drive their overall reaction network (metabolism). In most cells, these are separate pathways. There is only one biochemical pathway that serves all three needs simultaneously: the acetyl-CoA pathway of CO 2 fixation. In the acetyl-CoA pathway, electrons from H 2 reduce CO 2 to pyruvate for carbon supply, while methane or acetate synthesis are coupled to energy conservation as ATP. This simplicity and thermodynamic favorability prompted Georg Fuchs and Erhard Stupperich to propose in 1985 that the acetyl-CoA pathway might mark the origin of metabolism, at the same time that Steve Ragsdale and Harland Wood were uncovering catalytic roles for Fe, Co, and Ni in the enzymes of the pathway. Subsequent work has provided strong support for those proposals.In the presence of Fe, Co, and Ni in their native metallic state as catalysts, aqueous H 2 and CO 2 react specifically to formate, acetate, methane, and pyruvate overnight at 100 °C. These metals (and their alloys) thus replace the function of over 120 enzymes required for the conversion of H 2 and CO 2 to pyruvate via the pathway and its cofactors, an unprecedented set of findings in the study of biochemical evolution. The reactions require alkaline conditions, which promote hydrogen oxidation by proton removal and are naturally generated in serpentinizing (H 2 -producing) hydrothermal vents. Serpentinizing hydrothermal vents furthermore produce natural deposits of native Fe, Co, Ni, and their alloys. These are precisely the metals that reduce CO 2 with H 2 in the laboratory; they are also the metals found at the active sites of enzymes in the acetyl-CoA pathway. Iron, cobalt and nickel are relicts of the environments in which metabolism arose, environments that still harbor ancient methane- and acetate-producing autotrophs today. This convergence indicates bedrock-level antiquity for the acetyl-CoA pathway. In acetogens and methanogens growing on H 2 as reductant, the acetyl-CoA pathway requires flavin-based electron bifurcation as a source of reduced ferredoxin (a 4Fe4S cluster-containing protein) in order to function. Recent findings show that H 2 can reduce the 4Fe4S clusters of ferredoxin in the presence of native iron, uncovering an evolutionary precursor of flavin-based electron bifurcation and suggesting an origin of FeS-dependent electron transfer in proteins. Traditionally discussed as catalysts in early evolution, the most common function of FeS clusters in metabolism is one-electron transfer, also in radical SAM enzymes, a large and ancient enzyme family. The cofactors and active sites in enzymes of the acetyl-CoA pathway uncover chemical antiquity in metabolism involving metals, methyl groups, methyl transfer reactions, cobamides, pterins, GTP, S -adenosylmethionine, radical SAM enzymes, and carbon-metal bonds. The reaction sequence from H 2 and CO 2 to pyruvate on naturally deposited native metals is maximally simple. It requires neither nitrogen, sulfur, phosphorus, RNA, ion gradients, nor light. Solid-state metal catalysts tether the origin of metabolism to a H 2 -producing, serpentinizing hydrothermal vent.

Rubisco (D-ribulose 1,5-bisphosphate carboxylase/oxygenase) is the most abundant enzyme in the world, constituting up to half of the soluble protein content in plant leaves. Such is its ubiquity that its chemical fingerprint can be detected in the geological record spanning billions of years. Rubisco catalyses the conversion of inorganic CO 2 into organic sugars, which underpin almost all of the biosphere, including our entire food chain. Due to its central role in the global carbon cycle, rubisco has been the subject of intense research for over 50 years. Rubisco is often considered inefficient due to its slow rate of carboxylation compared with other central metabolism enzymes, and its promiscuous oxygenase activity, which competes with the productive carboxylation reaction. It is hoped that engineering improved CO 2 fixation will have significant advantages in agriculture and climate change mitigation. However, rubisco has proven difficult to engineer, with decades of efforts yielding limited results. Recent research has focused on reconstructing the evolutionary trajectory of rubisco to help elucidate its cryptic origins. Such evolutionary studies have led to a better understanding of both the origins of more complex rubisco forms and the broader relationship between rubisco's structure and function., Competing Interests: Declaration of interests The authors declare no competing interests., (Copyright © 2024 Elsevier Inc. All rights reserved.)

Pre-hospital end-tidal carbon dioxide (E t CO 2 ) monitoring and arterial to end-tidal carbon dioxide gradient (P a-Et CO 2 ) have been associated with mortality in patients with traumatic brain injury. Our study aimed to analyze the association between alveolar E t CO 2 or P a-Et CO 2 and mortality in patients admitted in intensive care unit (ICU) with neurological injuries. In our retrospective analysis from using large de-identified ICU databases (MIMIC-III and -IV and eICU databases), we included 2872 ICU patients with neurological injuries, identified according to the International Classification of Diseases (ICD-9 and -10), who underwent E t CO 2 monitoring. We performed logistic regression and extended Cox regression to assess the association between mortality and candidate covariates, including E t CO 2 and P a-Et CO 2 . In-hospital mortality was 26% (n = 747). In univariate analysis, both the P a-Et CO 2 gradient and E t CO 2 levels during the first 24 h were significantly associated with mortality (for a 1 mmHg increase: OR = 1.03 [CI 95 1.016-1.035] and OR = 0.94 [CI 95 0.923-0.953]; p < 0.001). The association remained significant in multivariate analysis. The time-varying evolution of EtCO 2 was independently associated with mortality (for a 1 mmHg increase: HR = 0.976 [CI 95 0.966-0.985]; p < 0.001). The time-varying P a-Et CO 2 gradient was associated with mortality only in univariate analysis. In neurocritical patients, lower E t CO 2 levels at admission and throughout the ICU stay were independently associated with mortality and should be avoided., (© 2024. The Author(s).)

Carbon dioxide rebreathing (CO 2 rebreathing) significantly influences respiratory drive and the work of breathing during BiPAP ventilation. We analyzed CO 2 movement during BiPAP ventilation to find a method of real time detection of CO 2 rebreathing without the need of CO 2 concentration measurement sampled from the circuit (method expensive and not routinely used). Observational study during routine care in 15 bed university hospital ICU. At 18 patients who required BiPAP ventilation, intubated or during noninvasive ventilation, during weaning period airflow, pressure and CO 2 concentration signals were registered on both sides of venting port and 17 respiratory parameters were measured or calculated for each of 4747 respiratory cycles analyzed. Based on CO 2 movement (expiration-inspiration sequences) 3 types of cycle were identified, type I and II do not induce rebreathing but type III does. To test differences between the 3 types ANOVA, t-tests, and canonical discriminant analysis (CDA) were used. Then a multilayer perceptron (MLP) network, a type of artificial neural network, using the above parameters (excluding CO 2 concentration) was applied to automatically identify the three types of respiratory cycles. Of the 4747 respiratory cycles, 1849 were type I, 1545 type II, and 1353 type III. ANOVA and t-tests showed significant differences between the types of respiratory cycles. CDA confirmed a correct apportionment of 93.9% of the cycles; notably, of 97.9% of type III. MLP automatically classified the respiratory cycles into the three types with 98.8% accuracy. Three types of respiratory cycles could be distinguished based on CO 2 movement during BiPAP ventilation. Artificial neural networks can be used to automatically detect respiratory cycle type III, the only inducing CO 2 rebreathing., (© 2024. The Author(s).)

Tropical forests account for over 50% of the global terrestrial carbon sink, but climate change threatens to alter the carbon balance of these ecosystems. We show that warming and drying of tropical forest soils may increase soil carbon vulnerability, by increasing degradation of older carbon. In situ whole-profile heating by 4 °C and 50% throughfall exclusion each increased the average radiocarbon age of soil CO 2 efflux by ~2-3 years, but the mechanisms underlying this shift differed. Warming accelerated decomposition of older carbon as increased CO 2 emissions depleted newer carbon. Drying suppressed decomposition of newer carbon inputs and decreased soil CO 2 emissions, thereby increasing contributions of older carbon to CO 2 efflux. These findings imply that both warming and drying, by accelerating the loss of older soil carbon or reducing the incorporation of fresh carbon inputs, will exacerbate soil carbon losses and negatively impact carbon storage in tropical forests under climate change., (© 2024. The Author(s).)

Nitrogenases are the only known enzymes that reduce molecular nitrogen (N 2 ) to ammonia. Recent findings have demonstrated that nitrogenases also reduce the greenhouse gas carbon dioxide (CO 2 ), suggesting CO 2 to be a competitor of N 2 . However, the impact of omnipresent CO 2 on N 2 fixation has not been investigated to date. Here, we study the competing reduction of CO 2 and N 2 by the two nitrogenases of Rhodobacter capsulatus , the molybdenum and the iron nitrogenase. The iron nitrogenase is almost threefold more efficient in CO 2 reduction and profoundly less selective for N 2 than the molybdenum isoform under mixtures of N 2 and CO 2 . Correspondingly, the growth rate of diazotrophically grown R. capsulatus strains relying on the iron nitrogenase notably decreased after adding CO 2 . The in vivo CO 2 activity of the iron nitrogenase facilitates the light-driven extracellular accumulation of formate and methane, one-carbon substrates for other microbes, and feedstock chemicals for a circular economy.

3-Hydroxypropionic acid (3-HP) is a highly sought-after platform chemical serving as a precursor to a variety of high value-added chemical products. In this study, we designed and constructed a novel light-powered in vitro synthetic enzymatic biosystem comprising acetyl-CoA ligase, acetyl-CoA carboxylase, malonyl-CoA reductase, and phosphotransferase to efficiently produce 3-HP through CO 2 fixation from acetate, a cost-effective and readily available substrate. The system employed natural thylakoid membranes (TMs) for the regeneration of adenosine triphosphate and nicotinamide adenine dinucleotide phosphate. Comprehensive investigations were conducted on the effects of buffer solutions, substrate concentrations, enzyme loading levels, and TMs loading levels to optimize the yield of 3-HP. Following optimization, a production of 0.46 mM 3-HP was achieved within 6 h from an initial 0.5 mM acetate, with a yield nearing 92%. This work underscores the simplicity of 3-HP production via an in vitro biomanufacturing platform and highlights the potential for incorporating TMs as a sustainable and environmentally friendly approach in biomanufacturing processes.

Lactococcus (Lc.) paracarnosus and the phylogenetically closely related Lc. carnosus species are common members of the microbiota in meat stored under modified atmosphere and at low temperature. The effect of these strains on meat spoilage is controversially discussed. While some strains are known to cause spoilage, others are being studied for their potential to suppress the growth of spoilage and pathogenic bacteria. In this study, Lc. paracarnosus DSM 111017 T was selected based on a previous study for its ability to suppress the growth of meat spoilers, including Brochothrix thermosphacta. The mechanism by which this bioprotective strain inhibits competing bacteria and how it contributes to spoilage are not yet known. To answer these two questions, we investigated the effect of four different headspace gas mixtures (simulated air (21 % O 2 /79 % N 2 ); HiOx-MAP (70 % O 2 /30 % CO 2 ); nonOx-MAP (70 % N 2 / 30 % CO 2 ); simulated vacuum (100 % N 2 ) and the presence of Brochothrix (B.) thermosphacta TMW 2.2101 on the growth and transcriptional response of Lc. paracarnosus DSM 111017 T when cultured on a meat simulation agar surface at 4 °C. Analysis of genes specifically upregulated by the gas mixtures used revealed metabolic pathways that may lead to different levels of spoilage metabolites production. We propose that under elevated oxygen levels, Lc. paracarnosus preferentially converts pyruvate from glucose and glycerol to uncharged acetoin/diacetyl instead of lactate to counteract acid stress. Due to the potential production of a buttery off-flavour, the strain may not be suitable as a protective culture in meat packaged under high‑oxygen conditions. 70 % N 2 / 30 % CO 2 , simulated vacuum- and the presence of Lc. paracarnosus inhibited the growth of B. thermosphacta TMW 2.2101. However, B. thermosphacta did not affect gene regulation of metabolic pathways in Lc. paracarnosus, and genes previously predicted to be involved in B. thermosphacta growth suppression were not regulated at the transcriptional level. In conclusion, the study indicates that the gas mixture used in packaging significantly affects the metabolism and spoilage potential of Lc. paracarnosus and its ability to inhibit B. thermosphacta growth., Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Victoria Werum reports financial support was provided by German Federal Ministry of Food and Agriculture. If there are other authors, they declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Author(s). Published by Elsevier B.V. All rights reserved.)

Ocean acidification (OA) caused by increased atmospheric carbon dioxide is affecting marine systems globally and is more extreme in coastal waters. A wealth of research to determine how species will be affected by OA, now and in the future, is emerging. Most studies are discrete and generally do not include the full life cycle of animals. Studies that include the potential for adaptation responses of animals from areas with different environmental conditions and the most vulnerable life stages are needed. Therefore, we conducted experiments with the widely distributed blue mussel, Mytilus edulis, from populations regularly exposed to different OA conditions. Mussels experienced experimental conditions prior to spawning, through embryonic and larval development, both highly vulnerable stages. Survivorship to metamorphosis of larvae from all populations was negatively affected by extreme OA conditions (pH 7.3, Ωar, 0.39, pCO2 2479.74), but, surprisingly, responses to mid OA (pH 7.6, Ωar 0.77, pCO21167.13) and low OA (pH 7.9, Ωar 1.53, pCO2 514.50) varied among populations. Two populations were robust and showed no effect of OA on survivorship in this range. One population displayed the expected negative effect on survivorship with increased OA. Unexpectedly, survivorship in the fourth population was highest under mid OA conditions. There were also significant differences in development time among populations that were unaffected by OA. These results suggest that adaptation to OA may already be present in some populations and emphasizes the importance of testing animals from different populations to see the potential for adaptation to OA., Competing Interests: Competing interests The authors declare no competing or financial interests., (© 2024. Published by The Company of Biologists Ltd.)

Aims: Activation of central respiratory chemoreceptors provides excitatory drive to both respiratory and sympathetic outputs. The enhanced respiratory-sympathetic coupling contributes to the onset and development of hypertension. However, the specific central targets and molecular mechanisms involved in this process remain elusive. This study aimed to investigate the role of acid-sensing ion channel 1 (ASIC1) in nucleus tractus solitarii (NTS) neurons in CO 2 -stimulated cardiorespiratory effects in spontaneously hypertensive rats (SHRs)., Main Methods: Respiration and blood pressure of conscious rats were recorded by whole-body plethysmography and telemetry, respectively. Western blot was used to detect the expression difference of ASIC1 protein in NTS region between Wistar-Kyoto (WKY) rats and SHRs. Excitability of NTS neurons were assessed by extracellular recordings., Key Findings: Compared to WKY rats, the enhanced CO 2 -stimulated cardiopulmonary effect and up-regulation of ASIC1 in the NTS were already observed in 4-week-old prehypertensive SHRs. Furthermore, specific blockade of ASIC1 effectively attenuated the CO 2 -stimulated increase in firing rate of NTS neurons in anesthetized adult SHRs. Intracerebroventricular injections of the ASIC1a blocker PcTx1 or knockdown Asic1 in NTS neurons significantly reduced the heightened CO 2 -stimulated ventilatory response, and diminished the CO 2 -stimulated increase in arterial pressure and heart rate in adult SHRs., Significance: These findings showed that dysregulated ASIC1 signaling in the NTS contribute to the exaggerated CO 2 -stimulated cardiorespiratory effects observed in SHRs., Competing Interests: Declaration of competing interest The authors declare that there are no conflicts of interest., (Copyright © 2024 Elsevier Inc. All rights reserved.)

Microalgae are considered as a potential source of bioactive compounds to be used in different fields including food and pharmaceutical industry. In this context, fatty acid esters of hydroxy-fatty acids (FAHFA) are emerging as a new class of compounds with anti-inflammatory and anti-diabetic properties. An existing gap in the field of algal research is the limited knowledge regarding the production of these compounds. Our research questions aimed to determine whether the microalga H. pluvialis can synthesize FAHFA and whether the production levels of these compounds are increased when cultivated in a CO 2 -rich environment. To answer these questions, we used a LC-QTOF/MS method for the characterization of FAHFA produced by H. pluvialis while an LC-MS/MS method was used for their quantitation. The cultivation conditions of H. pluvialis, which include the utilization of CO 2 , can result in a 10-50-fold increase in FAHFA production., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Thermophilic acetogenic bacteria have attracted attention as promising candidates for biotechnological applications such as syngas fermentation, microbial electrosynthesis, and methanol conversion. Here, we aimed to isolate and characterize novel thermophilic acetogens from diverse environments. Enrichment of heterotrophic and autotrophic acetogens was monitored by 16S rRNA gene-based bacterial community analysis. Seven novel Moorella strains were isolated and characterized by genomic and physiological analyses. Two Moorella humiferrea isolates showed considerable differences during autotrophic growth. The M. humiferrea LNE isolate (DSM 117358) fermented carbon monoxide (CO) to acetate, while the M. humiferrea OCP isolate (DSM 117359) transformed CO to hydrogen and carbon dioxide (H2 + CO2), employing the water-gas shift reaction. Another carboxydotrophic hydrogenogenic Moorella strain was isolated from the covering soil of an active charcoal burning pile and proposed as the type strain (ACPsT) of the novel species Moorella carbonis (DSM 116161T and CCOS 2103T). The remaining four novel strains were affiliated with Moorella thermoacetica and showed, together with the type strain DSM 2955T, the production of small amounts of ethanol from H2 + CO2 in addition to acetate. The physiological analyses of the novel Moorella strains revealed isolate-specific differences that considerably increase the knowledge base on thermophilic acetogens for future applications., (© The Author(s) 2024. Published by Oxford University Press on behalf of FEMS.)

Rubisco activity is highly regulated and frequently limits carbon assimilation in crop plants. In the chloroplast, various metabolites can inhibit or modulate Rubisco activity by binding to its catalytic or allosteric sites, but this regulation is complex and still poorly understood. Using rice Rubisco, we characterised the impact of various chloroplast metabolites which could interact with Rubisco and modulate its activity, including photorespiratory intermediates, carbohydrates, amino acids; as well as specific sugar-phosphates known to inhibit Rubisco activity - CABP (2-carboxy-d-arabinitol 1,5-bisphosphate) and CA1P (2-carboxy-d-arabinitol 1-phosphate) through in vitro enzymatic assays and molecular docking analysis. Most metabolites did not directly affect Rubisco in vitro activity under both saturating and limiting concentrations of Rubisco substrates, CO2 and RuBP (ribulose-1,5-bisphosphate). As expected, Rubisco activity was strongly inhibited in the presence of CABP and CA1P. High physiologically relevant concentrations of the carboxylation product 3-PGA (3-phosphoglyceric acid) decreased Rubisco activity by up to 30%. High concentrations of the photosynthetically derived hexose phosphates fructose 6-phosphate (F6P) and glucose 6-phosphate (G6P) slightly reduced Rubisco activity under limiting CO2 and RuBP concentrations. Biochemical measurements of the apparent Vmax and Km for CO2 and RuBP (at atmospheric O2 concentration) and docking interactions analysis suggest that CABP/CA1P and 3-PGA inhibit Rubisco activity by binding tightly and loosely, respectively, to its catalytic sites (i.e. competing with the substrate RuBP). These findings will aid the design and biochemical modelling of new strategies to improve the regulation of Rubisco activity and enhance the efficiency and sustainability of carbon assimilation in rice., (© 2024 The Author(s).)

To explore whether oxidative stress caused by 100% CO 2 is an inhibitory mechanism against Shewanella putrefaciens , the oxidative stress reaction, antioxidant activity, and damage to the cell membrane, protein, and DNA of CO 2 -incubated S. putrefaciens at 4 °C were evaluated. Research demonstrated that CO 2 caused more severe reactive oxygen species (ROS) accumulation. Simultaneously, weaker • OH/H 2 O 2 / O 2 •- -scavenging activity and decreased T-VOC and GSH content were also observed. The activities of antioxidant enzymes (SOD, POD, CAT, and GPX) continuously declined, which might be attributed to the CO 2 -mediated decrease in the pH value. Correspondingly, the cell membrane was damaged with hyperpolarization, increased permeability, and more severe lipid peroxidation. The expression of total and membrane protein decreased, and the synthesis and activity of extracellular protease were inhibited. DNA was also subjected to oxidative damage and expressed at a lower level. All results collaboratively confirmed that ROS excitation and inhibition of antioxidant activity were important inhibition mechanisms of CO 2 on S. putrefaciens .

Membrane technology advancements within the past twenty years have provided a new perspective on environmentalism as engineers design membranes to separate greenhouse gases from the environment. Several scientific journals have published articles of experimental evidence quantifying carbon dioxide (CO 2 ), a common greenhouse gas, separation using membrane technology and ranking them against one another. On the other hand, natural systems such as the respiratory system of mammals also accomplish transmembrane transport of CO 2 . However, to our knowledge, a comparison of these natural organic systems with engineered membranes has not yet been accomplished. The tracheal respiratory systems of insects transport CO 2 at the highest rates in the animal kingdom. Therefore, this work compares engineered membranes to the tracheal systems of insects by quantitatively comparing greenhouse gas conductance rates. We demonstrate that on a per unit volume basis, locusts can transport CO 2 approximately ∼100 times more effectively than the best current engineered systems. Given the same temperature conditions, insect tracheal systems transport CO 2 three orders of magnitude faster on average. Miniaturization of CO 2 capture systems based on insect tracheal system design has great potential for reducing cost and improving the capacities of industrial CO 2 capture., (© 2024 IOP Publishing Ltd.)

Indigenous communities in the North American Arctic are characterized by mixed economies that feature hunting, fishing, gathering, and trapping activities-and associated sharing practices-alongside the formal wage economy. The region is also undergoing rapid social, economic, and climate changes, including, in Canada, carbon taxation, which is impacting the cost of fuel used in local food harvesting. Because of the importance of local foods to nutrition, health, and well-being in Arctic Indigenous communities, there is an urgent need to better understand the sensitivity of Arctic food systems to social, economic, and climate changes and to develop plans for mitigating potential adverse effects. Here, we develop a Bayesian model to calculate the substitution value and carbon emissions of market replacements for local food harvests in the Inuvialuit Settlement Region, Canada. Our estimates suggest that under plausible scenarios, replacing locally harvested foods with imported market substitutes would cost over 3.1 million Canadian dollars per year and emit over 1,000 tons of CO 2 -equivalent emissions per year, regardless of the shipping scenario. In contrast, we estimate that gasoline inputs to harvesting cost approximately $295,000 and result in 315 to 497 tons of emissions. These results indicate that climate change policies that fail to account for local food production may undermine emissions targets and adversely impact food security and health in Arctic Indigenous communities, who already experience a high cost of living and high rates of food insecurity., Competing Interests: Competing interests statement:This article was developed from an impact report completed by E.R. under contract for the Inuvialuit Regional Corporation.

Nicotinamide adenine dinucleotide-dependent formate dehydrogenase from Candida boidinii was immobilized in a 1,2-dimyristoyl- sn -glycero-3-phosphocholine/cholesterol floating lipid bilayer on the gold surface as a biocatalyst for electrochemical CO 2 reduction. We report that, in contrast to common belief, the enzyme can catalyze the electrochemical reduction of CO 2 to formate without the cofactor protonated nicotinamide adenine dinucleotide. The electrochemical data indicate that the enzyme-catalyzed reduction of CO 2 is diffusion-controlled and is a reversible reaction. The orientation and conformation of the enzyme were investigated by surface-enhanced infrared reflection absorption spectroscopy. The α-helix of the enzyme adopts an orientation nearly parallel to the surface, bringing its active center close to the gold surface. This orientation allows direct electron transfer between CO 2 and the gold electrode. The results in this paper provide a new method for the development of enzymatic electrocatalysts for CO 2 reduction.

Background: A high minute ventilation/rate of carbon dioxide production (V̇ E /V̇co 2 ) slope during exercise is prognostic for cardiovascular death. Recent data indicate that adults with either controlled or untreated primary hypertension, but not those with uncontrolled hypertension, exhibit a higher V̇ E /V̇co 2 slope during exercise. However, the sample sizes were modest. Therefore, we used the Fitness Registry and the Importance of Exercise National Database to determine whether adults with hypertension, particularly those with controlled or untreated hypertension, exhibit higher V̇ E /V̇co 2 slopes compared with adults without hypertension., Methods and Results: Using the Fitness Registry and the Importance of Exercise National Database, we isolated primary hypertension by excluding those with any disease other than hypertension or taking any medications other than antihypertension medications. We also excluded current smokers and those with obesity. The V̇ E /V̇co 2 slope was determined during a peak cycling exercise test. All data are presented as median [interquartile range]. We compared groups using linear regression adjusted for age, male/female, and body mass index. The characteristics of the entire sample (n=4109) were age, 42 [18] years; 48% women; body mass index, 26 [4] kg/m 2 . The V̇ E /V̇co 2 slope did not differ between adults with hypertension (n=1940; 24.7 [3.7]) compared with those without hypertension (n=2169; 24.9 [3.8]) (hypertension versus no hypertension, P =0.31; overall model: R 2 =0.07, F 4,4104 =73.0; P <0.001). Further, the V̇ E /V̇co 2 slope did not differ between adults with medication-controlled hypertension (n=107; 24.4 [3.0]), untreated hypertension (n=1626; 24.8 [3.9]), uncontrolled hypertension (n=207; 24.8 [3.0]), or those without hypertension (n=2169; 24.9 [3.8]) (hypertension subgroup versus no hypertension, P ≥0.06; overall model: R 2 =0.07, F 6,4102 =49.6, P <0.001)., Conclusions: Primary hypertension is not associated with V̇ E /V̇co 2 slope in the Fitness Registry and the Importance of Exercise National Database.