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Photosynthetic microorganisms such as cyanobacteria, microalgae, and anoxygenic phototrophic bacteria (APB) have emerged as sustainable and economic biotechnology platforms due to their ability to transform energy from light into chemicals through photosynthesis. The light is absorbed by photosynthetic pigment-protein antenna complexes which are composed of pigments such as bacteriochlorophylls (BChl) and carotenoids in APB, and chlorophylls (Chl), phycobiliproteins (PBP), and carotenoids in cyanobacteria and microalgae. These photosynthetic pigments are essential in the physiology of photosynthetic microorganisms and offer significant health benefits due to their potent antioxidant activity, with properties that include anticancer, antiaging, antiproliferative, anti-inflammatory, and neuroprotective effects. This review first provides an overview of current advances in photosynthetic pigment synthesis and the latest strategies to increase pigment content in cyanobacteria, microalgae, and APB. It then delves into the pigment production process, covering biosynthetic pathways, critical environmental parameters, and extraction methods. Finally, the potential marketability of photosynthetic pigments together with current limitations are discussed., 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 © 2025 The Authors. Published by Elsevier B.V. All rights reserved.)

In this study, the performance of a pilot-scale biotrickling filter (BTF) for anoxic hydrogen sulfide (H 2 S) removal from real biogas was evaluated over 226 days. The BTF, inoculated with activated sludge from a nearby wastewater treatment plant, operated in an industrial environment with raw biogas from an anaerobic digester fed with municipal solid waste. The operating strategy was based on controlling nitrate consumption by sulfur-oxidizing nitrate-reducing (SO-NR) bacteria. H 2 S-inlet loads (H 2 S-IL) ranged from 0.43 to 61.73 g S-H 2 S m³ h⁻¹ , with biogas flow rates between 0.25 and 3.5 m³ h⁻¹ and H 2 S concentration peaks of 11,000 ppm v . The pH was maintained at 7.0 using a 25 %v·v⁻¹ NaOH solution. The H 2 S removal efficiency (H 2 S-RE) exceeded 93.9 % for most of the period, with a maximum elimination capacity of 35.17 g S-H 2 S m⁻³ h⁻¹ at an IL of 37.20 g S-H 2 S m⁻³ h⁻¹ (H 2 S-RE > 95 %). Sulfate selectivity was over 85 % during normal operation. High H 2 S-IL led to excessive elemental sulfur accumulation without nitrate, which was later oxidized to sulfate during low H 2 S-IL periods, preventing maintenance shutdowns. Overall, the results demonstrate the efficacy of anoxic BTFs in removing H 2 S under variable biogas conditions at a pilot scale., Competing Interests: Declaration of Competing Interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Raquel Lebrero reports financial support was provided by University of Valladolid. Raquel Lebrero reports financial support was provided by European Union. Raquel Lebrero reports financial support was provided by Regional Government of Castilla y Leon. 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 B.V. All rights reserved.)

Current challenges in biopharmaceutical manufacturing, such as ectoine production, include high operational costs and limited availability. Transitioning to processes that valorize renewable carbon sources like CO 2 into ectoine can make production more sustainable and accessible to the economy and society. However, cell platforms that produce ectoine with CO 2 still require bioprocess optimization and resilient microorganisms able to continuously maintain high ectoine yields and CO 2 removals. A comprehensive screening of cultivation and operational strategies was conducted in six stirred-tank gas bioreactors using the strain Hydrogenovibrio marinus , a halophilic, fast-growing, hydrogenotrophic bacterium with low nutrient requirements. Gas residence times of 120 min at gas ratios of 10:40:50 CO 2 :H 2 :air (% v/v) and dilution rates of 0.25 d -1 boosted ectoine production and biomass growth during long-term operation. Under these conditions, ectoine productivity reached 5.0 ± 0.3 g m -3 d -1 , with maximum specific ectoine contents of 134.0 ± 6.3 mg Ect g biomass -1 , achieving yields similar to heterotrophic strains. This study demonstrates for the first time the feasibility of integrating ectoine production with continuous CO 2 abatement using H 2 as a clean and hazard-free energy source, which marks a significant advancement in sustainable ectoine manufacturing and CO 2 circularity.

Syngas from the gasification of organic wastes represents a promising feedstock for fostering a sustainable bioeconomy. However, its potential is currently constrained by the low-value products generated. Osmolytes, such as hydroxyectoine, are high-value compounds, however, their biological production as isolated osmolytes is not yet cost-effective. This study utilized shotgun genomics and laboratory validation to find a carboxydotrophic, halotolerant bacterium, Hydrogenibacillus schlegelii, that could produce hydroxyectoine using H 2 , CO and CO 2 as the sole source of energy and carbon. Subsequently, NaCl concentration, temperature and syngas composition were optimized in semi-continuous bioreactors. Optimal conversion of CO into hydroxyectoine occurred at a gas composition of 70 %:10 % CO:H 2 (v/v) (44.8 ± 10.1 mg hydroxyectoine ·g biomass -1 ). NaCl concentrations of 5 % significantly enhanced hydroxyectoine content (46.7 ± 9.5 mg hydroxyectoine ·g biomass -1 ), but negatively affected gas consumption. This study opens new perspectives for the valorisation of syngas into hydroxyectoine, and for new cell platforms for pharmaceutical production based on syngas., 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.)

This study evaluated the influence of nanoparticles in both suspension and solid format on the performance of a microalgal process devoted to photosynthetic biogas purification. The experimental system consisted of an enclosed tubular photobioreactor coupled to a biogas absorption column through a mixing chamber. The high NH 4 + concentration in the inlet mineral medium (530 mg N-NH 4 + L -1 ) and the punctual addition of 115 mL of nanoparticle suspension to the system caused inhibition of the microalgal-bacterial cultivation. Conversely, cultivation broth aeration (0.5 L min -1 air flowrate) allowed the biomethane production fulfilling the EN 16723 (CH 4  > 90 %, CO 2  < 2 %). The nanoparticle suspension performance was superior to that of their solid counterparts in terms of CO 2 removal efficiency at equivalent nanoparticle dose (77 % vs. 49 %). However, parameters such as the nanoparticle suspension dosage and biomass concentration in the photobioreactor should be optimized to further improve biomethane quality before its industrial application., 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.)

Today, the use of biogas to produce more sustainable bioproducts is attracting an increasing attention in the quest for a circular economy. This work aims at optimizing the biosynthesis of high value bioproducts such as ectoine and hydroxyectoine from methane using a high mass transfer Taylor flow reactor and a methanotrophic consortium. The influence of the gas residence time (30-240 min) and concentration of microorganisms (0.1-1.8 g TSS·L -1 ) on methane bioconversion and ectoine production was evaluated. The maximum methane bioconversion efficiency reached was ∼90% at a gas residence time of 240 min. Biological limitation in the reactor was observed at concentrations below 0.5 g total suspended solids (TSS)·L -1 . The intracellular ectoine and hydroxyectoine content did not experience large variations with the gas residence time and biomass concentration. The maximum ectoine content was 49.0 ± 16.1 mg EC ·g TSS -1 at a gas residence time of 240 min and a biomass concentration of 0.7 g TSS·L -1 . The maximum hydroxyectoine content was 13.0 ± 3.6 and 12.7 ± 2.2 mg HE ·g TSS -1 at a gas residence time of 240 min and biomass concentrations of 1.8 and 1.2 g TSS·L -1 , respectively. Methylophaga and Methylomicrobium were the dominant methanotrophs in the bioreactor regardless of the gas residence time and biomass concentration. Microorganisms belonging to the genera Paracoccus, Methylophaga, Methylomicrobium and Nitratireductor have been identified as ectoines producers or have been found to possess genes responsible for ectoines synthesis., 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.)

Siloxanes (VMS) represent a class of organosilicon compounds known for their adverse effects on both the environment and human health. Their presence in biogas significantly hinders its economic valorisation, highlighting the need for effective treatment methods. This study investigates the performance of three different packing materials in the anoxic biofiltration of VMS (L2, L3, D4 and D5). The materials evaluated included plastic rings (BTF-1), polyurethane foam (BTF-2) and plastic rings combined with activated carbon (80:20) (BTF-3). Among them, BTF-3 exhibited superior performance, achieving maximum VMS removal efficiencies (REs) of 90%, including the complete elimination of L3 and D4, and ∼80% removal of D5, attributed to the presence of activated carbon. However, the abatement of L2 was inferior to that of other VMS (<80%), which was attributed to the activated carbon's affinity for larger molecular weights and critical diameters. In contrast, BTF-1 and BTF-2 supported maximum VMS removals of 40%. Notably, neither increasing the trickling liquid velocity from 2 to 4.5 m h⁻ 1 nor adding Fe-carbon nanoparticles to the solution had any impact on the BTFs' performance. Following the successful results observed in BTF-3, gas residence time was reduced from 60 to 42 min, consequently leading to an increase in the EC from 366 to 509 mg m -3 h -1 (corresponding to an RE = 87%). Despite the different performance of the BTFs, comparable bacterial communities were identified, dominated by the genera Thermomonas, Corynebacterium, Aquimonas, Thauera and Parvibaculum. The results obtained in this study highlighted the potential of activated carbon as packing material for enhancing abatement performance during biotrickling filtration and identified new bacterial genera with potential for VMS degradation., 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.)

Volatile organic compounds (VOCs) emitted into the atmosphere negatively affect the environment and human health. Biotrickling filtration, an effective technology for treating VOC-laden waste gases, faces challenges in removing hydrophobic VOCs due to their low water solubility and therefore limited bioavailability to microorganisms. Consequently, the addition of (bio)surfactants has proven to be a promising strategy to enhance the removal of hydrophobic VOCs in biotrickling filters (BTFs). Yet, up to now, no single study has ever performed a mass transfer characterization of a BTF under (bio)surfactants addition. In this study, the effect of (bio)surfactant addition on the gas-liquid mass transfer characteristics of two BTFs was measured by using oxygen (O 2 ) as a model gas. Through an empirical correlation, the mass transfer coefficients (k L a) of two hydrophobic VOCs, toluene and hexane, which are of industrial and environmental significance, were estimated. One BTF was filled with expanded perlite, while the other with a mixture of compost and wood chips (C + WC). Both BTFs were operated under different liquid velocities (U L : 0.95 and 1.53 m h -1 ). Saponin, a biological surfactant, and Tween 80, a synthetic surfactant, were added to the recirculating liquid at different critical micelle concentrations (CMCs: 0-3 CMC). The higher interfacial and surface area of the perlite BTF compared to the C + WC BTF led to higher k L aO 2 values regardless of the operational condition: 308 ± 18-612 ± 19 h -1 versus 42 ± 4-177 ± 24 h -1 , respectively. Saponin addition at 0.5 and 1 CMC had positive effects on the perlite BTF, with k L aO 2 values two times higher compared to those at 0 CMC. Tween 80 exhibited a neutral or slightly positive effect on the mass transfer of both BTFs under all conditions. Overall, the CMC, along with the physical characteristics of the packing materials and the operational conditions evaluated explained the results obtained. This study provides fundamental data essential to improve the performance and design of BTFs for hydrophobic VOCs abatement., 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.)

The present study evaluated the production potential of CH 4 , carboxylic acids and alcohols from a mixed culture enriched using synthetic syngas. The influence of syngas concentration on the microbial community and products productivity and selectivity was investigated. The results demonstrated the enrichment of a mesophilic mixed culture capable of converting CO and H 2 mainly to CH 4 and acetate, along with butyrate. The selectivity values showed that acetate production was enhanced during the first cycle in all conditions tested (up to 20 %), while CH 4 was the main product generated during following cycles. Concretely, CH 4 selectivity remained unaffected by syngas concentration, reaching a stable value of 41.6 ± 2.0 %. On the other hand, butyrate selectivity was only representative at the highest syngas concentration and lower pH values (26.1 ± 5.8 %), where the H 2 consumption was completely inhibited. Thus, pH was identified as a key parameter for both butyrate synthesis and the development of hydrogenotrophic activity., 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.)

Bioactive coatings are envisaged as a promising biotechnology to tackle the emerging problem of indoor air pollution. This solution could cope with the low concentrations, the wide range of compounds and the hydrophobicity of some indoor air VOCs, which are the most important bottlenecks regarding the implementation of conventional biotechnologies for indoor air treatment. A bioactive coating-based bioreactor was tested in this study for the abatement of different VOCs (n-hexane, toluene and α-pinene) at different empty bed residence times (EBRT) and inlet VOC concentrations. The performance of this reactor was compared with a conventional biofilm-based bioreactor operated with the same microbial inoculum. After an acclimation period, the bioactive coating-based bioreactor achieved abatements of over 50% for hexane, 80% for toluene and 70% for pinene at EBRTs of 112-56 s and inlet concentrations of 9-15 mg m -3 . These results were about 25, 10 and 20% lower than the highest removals recorded in the biofilm-based bioreactor. Both bioreactors experienced a decrease in VOC abatement by ∼25% for hexane, 45% for toluene and 40% for pinene, after reducing the EBRT to 28 s. When inlet VOC concentrations were progressively reduced, VOC abatement efficiencies did not improve. This fact suggested that low EBRTs and low inlet VOCs concentration hindered indoor air pollutant abatement as a result of a limited mass transfer and bioavailability. Metagenomic analyses showed that process operation with toluene, hexane and pinene as the only carbon and energy sources favored an enriched bacterial community represented by the genera Devosia, Mesorhizobium, Sphingobacterium and Mycobacterium, regardless of the bioreactor configuration. Bioactive coatings were used in this work as packing material of a conventional bioreactor, achieving satisfactory VOC abatement similar to a conventional bioreactor., 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 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Nowadays, people spend 80-90% of their time indoors, while recent policies on energy efficient and safe buildings require reduced building ventilation rates and locked windows. These facts have raised a growing concern on indoor air quality, which is currently receiving even more attention than outdoors pollution. Prevention is the first and most cost-effective strategy to improve indoor air quality, but once pollution is generated, a battery of physicochemical technologies is typically implemented to improve air quality with a questionable efficiency and at high operating costs. Biotechnologies have emerged as promising alternatives to abate indoor air pollutants, but current bioreactor configurations and the low concentrations of indoor air pollutants limit their widespread implementation in homes, offices and public buildings. In this context, recent investigations have shown that potted plants can aid in the removal of a wide range of indoor air pollutants, especially volatile organic compounds (VOCs), and can be engineered in aesthetically attractive configurations. The original investigations conducted by NASA, along with recent advances in technology and design, have resulted in a new generation of botanical biofilters with the potential to effectively mitigate indoor air pollution, with increasing public aesthetics acceptance. This article presents a review of the research on active botanical filters as sustainable alternatives to purify indoor air., 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 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Biogas biorefineries have opened up new horizons beyond heat and electricity production in the anaerobic digestion sector. Added-value products such as polyhydroxyalkanoates (PHAs), which are environmentally benign and potential candidates to replace conventional plastics, can be generated from biogas. This work investigated the potential of an innovative two-stage growth-accumulation system for the continuous production of biogas-based polyhydroxybutyrate (PHB) using Methylocystis hirsuta CSC1 as cell factory. The system comprised two turbulent bioreactors in series to enhance methane and oxygen mass transfer: a continuous stirred tank reactor (CSTR) and a bubble column bioreactor (BCB) with internal gas recirculation. The CSTR was devoted to methanotrophic growth under nitrogen balanced growth conditions and the BCB targeted PHB production under nitrogen limiting conditions. Two different operational approaches under different nitrogen loading rates and dilution rates were investigated. A balanced nitrogen loading rate along with a dilution rate (D) of 0.3 day -1 resulted in the most stable operating conditions and a PHB productivity of ~53 g PHB m -3 day -1 . However, higher PHB productivities (~127 g PHB m -3 day -1 ) were achieved using nitrogen excess at a D = 0.2 day -1 . Overall, the high PHB contents (up to 48% w/w) obtained in the CSTR under theoretically nutrient balanced conditions and the poor process stability challenged the hypothetical advantages conferred by multistage vs single-stage process configurations for long-term PHB production., (© 2023 The Authors. Biotechnology and Bioengineering published by Wiley Periodicals LLC.)

The effect of alkali-based pretreatment on the methanization of bioplastics was investigated. The tested bioplastics included PHB [poly(3-hydroxybutyrate)], PHBH [poly(3-hydroxybutyrate-co-3-hydroxyhexanoate)], PHBV [poly(3-hydroxybutyrate-co-3-hydroxyvalerate], PLA (polylactic acid), and a PLA/PCL [poly(caprolactone)] 80/20 blend. Prior to methanization tests, the powdered polymers (500-1000 μm) at a concentration of 50 g/L were subjected to alkaline pretreatment using NaOH 1 M for PLA and PLA/PCL, and NaOH 2 M for PHB-based materials. Following 7 days of pretreatment, the amount of solubilized carbon for PLA and its blend accounted for 92-98% of the total initial carbon, while lower carbon recoveries were recorded for most PHB-based materials (80-93%), as revealed by dissolved total organic carbon analysis. The pretreated bioplastics were then tested for biogas production by means of mesophilic biochemical methane potential tests. Compared to unpretreated PHBs, methanization rates of pretreated PHBs were accelerated by a factor of 2.7 to 9.1 with comparable (430 NmL CH 4 /g material feed) or slightly lower (15% in the case of PHBH) methane yields, despite featuring a 1.4-2.3 times longer lag phases. Both materials, PLA and the PLA/PCL blend, were only extensively digested when pretreated, yielding about 360-380 NmL CH 4 per gram of material fed. Unpretreated PLA-based materials showed nearly zero methanization under the timeframe and experimental conditions tested. Overall, the results suggested that alkaline pretreatment can help to enhance the methanization kinetics of bioplastics., Competing Interests: Declaration of Competing Interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: O.G.-D., L.J.M.-M.,S.R.-V.,R.L.,R.A.B.,T.B.,R.M. reports financial support was provided by Société des Produits Nestlé S.A. R.A.B. reports a relationship with Société des Produits Nestlé S.A. that includes: employment. T.B. was employed by Société des Produits Nestlé S.A. during the development of this research., (Copyright © 2023 The Authors. Published by Elsevier Ltd.. All rights reserved.)

In recent years, a number of microbial enzymes capable of degrading plastics have been identified. Biocatalytic depolymerization mediated by enzymes has emerged as a potentially more efficient and environmentally friendly alternative to the currently employed methods for plastic treatment and recycling. However, the functional and systematic study of depolymerase enzymes with respect to the degradation of a series of plastic polymers in a single work has not been widely addressed at present. In this study, the ability of a set of enzymes (esterase, arylesterase and cutinase) to degrade commercial biodegradable polymers (PBS, PBAT, PHB, PHBH, PHBV, PCL, PLA and PLA/PCL) and the effect of pre-treatment methods on their degradation rate was assessed. The degradation products were identified and quantified by HPLC and LC-HRMS analysis. Out of the three enzymes, Fusarium solani cutinase (FsCut) showed the highest activity on grinded PBAT, PBS and PCL after 7 days of incubation. FsCut was engineered and heterologous expressed in Escherichia coli , which conferred the bacterium the capability of degrading solid discs of PBAT and to grow in PBS as the sole carbon source of the medium.

The abatement of indoor volatile organic compounds (VOCs) represents a major challenge due to their environmental risk, wide nature and concentration variability. Biotechnologies represent a cost-effective, robust and sustainable platform for the treatment of hazardous VOCs at low and fluctuating concentrations. However, they have been scarcely implemented for indoor air purification. Thus, little is known about the influence of the reactor configuration or the VOC nature and concentration variability on the removal, resilience and the microbial population of bioreactor configurations susceptible to be implemented, both in indoors and industrial environments. The present study aims at comparing the removal performance of four VOCs with different hydrophobicity and molecular structure -acetone, n-hexane, α-pinene and toluene-at two inlet concentrations (5 and 400 mg m -3 ), which mimics the concentrations of contaminated indoor and industrial air. To this aim a stirred tank, flat biofilm and latex-based biocoated flat bioreactor were comparatively evaluated. The results demonstrated the superior performance of the stirred tank reactor for the removal of hydrophilic VOCs at high inlet concentrations, which achieved removals >99% for acetone and toluene. At low concentrations, the removal efficiencies of acetone, toluene and α-pinene were >97% regardless of the bioreactor configuration tested. The most hydrophobic gas, n-hexane, was more efficiently removed in the flat biofilm reactor without latex. The microbial community analyses showed that the presence of VOCs as the only carbon and energy source didn't promote the growth of dominant bacterial members and the populations independently evolved in each reactor configuration and operation mode. The fungal population was more diverse in the biofilm-based bioreactors, although, it was mainly dominated by uncultured fungi from the phylum Cryptomycota., 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 © 2022 The Authors. Published by Elsevier Ltd.. All rights reserved.)

This study aims at investigating the influence of operational parameters on biohydrogen production from fruit-vegetable waste (FVW) via lactate-driven dark fermentation. Mesophilic batch fermentations were conducted at different pH (5.5, 6.0, 6.5, 7.0, and non-controlled), total solids (TS) contents (5, 7, and 9%) and initial cell biomass concentrations (18, 180, and 1800 mg VSS/L). Higher hydrogen yields and rates were attained with more neutral pH values and low TS concentrations, whereas higher biomass densities enabled higher production rates and avoided wide variations in hydrogen production. A marked lactate accumulation (still at neutral pH) in the fermentation broth was closely associated with hydrogen inhibition. In contrast, enhanced hydrogen productions matched with much lower lactate accumulations (even it was negligible in some fermentations) along with the acetate and butyrate co-production but not with carbohydrates removal. At pH 7, 5% TS, and 1800 mg VSS/L, 49.5 NmL-H 2 /g VS fed and 976.4 NmL-H 2 /L-h were attained., 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 © 2022 The Author(s). Published by Elsevier Ltd.. All rights reserved.)

The hazard and operability analysis (HAZOP) is one of the most popular approaches for risk management, although weaknesses such as the limited number of risk factors considered, the inaccuracy of experts' opinions or the limited process knowledge might compromise the quality of the results. In this context, conventional HAZOP analysis can be improved via a Fuzzy Multi-Attribute HAZOP technique. Under a fuzzy logic, Analytic Hierarchy Process and the Technique for Order of Preference by Similarity to Ideal Solution can be combined with Fuzzy Multi-Attribute HAZOP to determine the weight of risk factors and to rank critical hazards. The inherent risks biogas upgrading, such as explosiveness, overpressure, or premature deterioration of equipment, should be identified for planning of critical control points and for enabling a proper maintenance plan. Previous models were applied to a photosynthetic biogas upgrading and a biogas-to-polyhydroxyalkanoates production pilot plant in order to identify and get more information about associated risks of the operation of these valorization biotechnologies, sometimes not fully provided by HAZOP analysis. Biotrickling filter and the polyhydroxyalkanoates production tank were identified as the most critical subsystems, with contributions of 33.3% and 17.8% to the overall risk, respectively (within quartile 1, Q 1 ). Additionally, biogas and recycling/feeding streams clustered a large number of operational risks (up to 83.4% of total risk within Q 1 ). The sensibility analysis demonstrated the reliability and robustness of the final ranking. The results of this analysis will support preventive maintenance by identifying critical monitored points when scaling-up biological biogas upgrading processes., 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 © 2022 The Authors. Published by Elsevier Ltd.. All rights reserved.)

The feasibility of producing volatile fatty acids (VFAs) from five commercial bioplastics via acidogenic fermentation by a non-pretreated anaerobic sludge was investigated. Mesophilic, anaerobic, acidogenic batch assays at 1, 10 and 20 g/L feed concentrations revealed the feasibility of producing VFAs from polyhydroxyalkanoates (PHA), i.e., PHB and PHBV, but not from PBS, PCL and PLA under the test conditions and time. However, only high PHA substrate concentrations (10-20 g/L) resulted in organic overloading and decreasing the pH of the culture broth down to 4-5, which in turn induced the accumulation of VFAs via kinetic imbalance between acidogenesis and methanogenesis. Gaseous carbon (C-CO 2 and C-CH 4 ) accounted for 8-35% of the total initial carbon, while C-VFAs represented 10-18%, mainly as acetate and butyrate. This study represents the first systematically assessed proof-of-concept to produce VFAs from PHA, which is key for the design of bioplastic-to-bioplastic recycling (bio)technologies., (Copyright © 2022 The Authors. Published by Elsevier Ltd.. All rights reserved.)

In regions highly dependent on fossil fuels imports, biomethane represents a promising biofuel for the transition to a bio-based circular economy. While biomethane is typically produced via anaerobic digestion and upgrading, biomethanation of the synthesis gas (syngas) derived from the gasification of recalcitrant solid waste has emerged as a promising alternative. This work presents a comprehensive and in-depth analysis of the state-of-the-art and most recent advances in the field, compiling the potential of this technology along with the bottlenecks requiring further research. The key design and operational parameters governing syngas production and biomethanation (e.g. organic feedstock, gasifier design, microbiology, bioreactor configuration, etc.) are critically analysed., (Copyright © 2022 The Authors. Published by Elsevier Ltd.. All rights reserved.)

The design of efficient cultivation strategies to produce bioplastics from biogas is crucial for the implementation of this biorefinery process. In this work, biogas-based polyhydroxybutyrate (PHB) production and CH 4 biodegradation performance was investigated for the first time in a stirred tank bioreactor inoculated with Methylocystis parvus str. OBBP. Decreasing nitrogen loading rates in continuous mode and alternating feast:famine regimes of 24 h-cycles, and alternating feast:famine regimes of 24 h:24 h and 24 h:48 h were tested. Continuous N feeding did not support an effective PHB production despite the occurrence of nitrogen limiting conditions. Feast-famine cycles of 24 h:24 h (with 50% stoichiometric nitrogen supply) supported the maximum PHB production (20 g-PHB m -3 d -1 ) without compromising the CH 4 -elimination capacity (25 g m -3 h -1 ) of the system. Feast:famine ratios ≤1:2 entailed the deterioration of process performance at stoichiometric nitrogen inputs ≤60%., (Copyright © 2022 The Authors. Published by Elsevier Ltd.. All rights reserved.)

α-hemolysin (HlyA) of E. coli binds irreversibly to human erythrocytes and induces cell swelling, ultimately leading to hemolysis. We characterized the mechanism involved in water transport induced by HlyA and analyzed how swelling and hemolysis might be coupled. Osmotic water permeability (P f ) was assessed by stopped-flow light scattering. Preincubation with HlyA strongly reduced P f in control- and aquaporin 1-null red blood cells, although the relative P f decrease was similar in both cell types. The dynamics of cell volume and hemolysis on RBCs was assessed by electrical impedance, light dispersion and hemoglobin release. Results show that HlyA induced erythrocyte swelling, which is enhanced by purinergic signaling, and is coupled to osmotic hemolysis. We propose a mathematical model of HlyA activity where the kinetics of cell volume and hemolysis in human erythrocytes depend on the flux of osmolytes across the membrane, and on the maximum volume that these cells can tolerate. Our results provide new insights for understanding signaling and cytotoxicity mediated by HlyA in erythrocytes.