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Haematococcus pluvialis (H. pluvialis) can naturally accumulate high amounts of astaxanthin – a powerful antioxidant. However, complete recovery of astaxanthin from the cysts of H. pluvialis is challenging because of the presence of a robust acetolysis resistant cell wall. Herein, a simple and effective planetary ball-milling pretreatment was developed to rupture the cells to attain an almost complete recovery of astaxanthin from H. pluvialis, using a supercritical CO2 and conventional organic solvent-based extraction. An optimized pretreatment using planetary ball mill under very mild conditions (150 rpm, 60 min) allowed the recovery of 31.4 mg/g dry weight of astaxanthin from H. pluvialis, while slightly harsh milling (500 rpm) was found to be detrimental toward astaxanthin. The extracts in acetone exhibited higher antioxidant activity in 1-diphenyl-2-picrylhydrazyl assay than those in dichloromethane. These mild conditions were safe and highly effective for the complete extraction of astaxanthin along with the others extractables. This study opens a new avenue for the efficient recovery of valuable thermolabile ketocarotenoid species from microalgae, which can be applied to the development of economically viable biorefineries. [ABSTRACT FROM AUTHOR]

Chlorella sorokiniana is a thermo-resistant microalga that is widely used for production of biofuel such as biodiesel. When cultured at 37°C under autotrophic conditions, C. sorokiniana showed the highest production of biomass, whereas the cells exhibited the highest production of fatty acids at 30°C. Herein, culture temperature shift was applied to improve autotrophic biodiesel production via the two-stage strategy. In addition, in order to increase biomass production, dissolved inorganic carbon source (mainly bicarbonate ion species), which is essential for photosynthesis, was supplied in the cultures by dissolving the CO2 in alkaline solution. As a result, cell growth increased up to 22% compared to that of the control cells by supplying constant inorganic carbon source into the cultures. The cells cultured under the condition of temperature shift (37°C to 30°C) and bicarbonate solution showed an increase in biodiesel productivity by 31% when compared to the cells that were cultured without such temperature adjustment (37°C to 37°C). In brief, our temperature shift method with bicarbonate buffer system (inorganic carbon supply) will improve biofuel production including biodiesel from C. sorokiniana under autotrophic conditions. [ABSTRACT FROM AUTHOR]

The aim of this work was to develop a new approach for simple and high-throughput selection of astaxanthin-hyperproducing Haematococcus mutants through a sequential combination method of azide-based colorimetric assessment and oil-based astaxanthin quantification. Randomly mutagenized cells were spotted on solid culture medium containing 50 µM of sodium azide to accelerate the biosynthesis of astaxanthin. After 3 days, highly-induced mutants were preliminarily isolated by visual inspection and their astaxanthin accumulations were rapidly quantified by soybean oil-based extraction method. On the whole, the selected mutants showed reduced vegetative growth rates but eventually exhibited higher astaxanthin productions than the parental strain owing to their improved inductive growths. Among them, M13 showed 174.7 ± 5.69 mg L −1 of the highest astaxanthin production, which is 1.59-times higher than that of wild-type. This wide-scope screening method expedites both upstream and downstream astaxanthin quantification, making it a useful tool for isolating microalgae with high astaxanthin production. [ABSTRACT FROM AUTHOR]

The aim of this study is investigate the effect of column diameter (D), height/diameter (H/D) ratio, and gas flow rate on microalgae cultivation, Haematococcus pluvialis . Bubble column reactors with various D and H/D ratio were tested to assess the hydrodynamic properties and biomass production performance. Then, H. pluvialis was cultured under outdoor autotrophic conditions using industrial flue gas. By optimizing the reactor module, reactor volume increased to 354% with minimized biomass loss. Compared to the control, developed module showed biomass and astaxanthin productivity of 0.052 versus 0.053 g/L/day, and 1.48 versus 1.47 mg/L/day, respectively. Consequently, biomass productivity was maintained with increased reactor scale, and the result is applicable to the scale up of overall microalgae cultivation process. [ABSTRACT FROM AUTHOR]

Under autotrophic conditions, starch plays an important role in establishing anoxic conditions during PSII-dependent hydrogen (H 2 ) photoproduction in microalgae. This is because starch is the sole organic substrate during respiratory consumption of internal oxygen (O 2 ) from PSII-dependent direct pathway. Herein, we propose a novel approach to further facilitate the internal starch synthesis of Chlamydomonas reinhardtii through the operation of carbon-concentrating mechanism (CCM) along with a two-stage process based on sulfur (S) deprivation, thereby resulting in enhanced anaerobic capacity during PSII-dependent H 2 photoproduction. When CCM-induced cells were exposed to high levels of carbon dioxide (CO 2 ) (5%, v/v) with S deprivation, internal levels of starch were significantly elevated by retaining a functional CCM with the boosted photosynthetic activity during 24 h of O 2 evolution phase (I) of S deprivation. Consequently, during H 2 production phase of S deprivation at irradiance of 50 μE m −2 s −1 , the concentrations of starch and H 2 in CCM-induced cells were remarkably enhanced by 65.0% and 218.9% compared to that of CCM-uninduced cells, respectively. The treatment of low-CO 2 -driven CCM induction prior to S deprivation is a cost-effective and energy-efficient strategy that significantly improves the solar-driven H 2 production by microalgae; this is particularly realizable in an industrial scale. [ABSTRACT FROM AUTHOR]

The negative effect of heat stress on the autotrophic astaxanthin production by Haematococcus pluvialis has been observed during outdoor culture in summer. Under the summer conditions, the proliferation of vegetative cells was highly halted in the green stage and the inducibility in the biosynthesis of astaxanthin was partly hindered in the red stage. Herein, under outdoor summer conditions in which variations of the diurnal temperature occur, heat-stress-driven inefficient vegetative growth of H. pluvialis was highly improved by inoculating the red cyst cells; thereby, maintaining relatively moderate intracellular carotenoid levels in the green stage. Subsequently, a remarkably enhanced astaxanthin titer was successfully obtained by supplementing 50 μM iron(II) to induce the heat stress-driven Haber–Weiss reaction in the red stage. As a result, the productivity of astaxanthin in the cells cultured under summer temperature conditions (23.4–33.5 °C) using the two methods of red cell (cyst) inoculation and the iron(Fe 2+ ) supplementation was increased by 147% up to 5.53 mg/L day compared with that of the cells cultured under spring temperature conditions (17.5–27.3 °C). Our technical solutions will definitely improve the annual natural astaxanthin productivity in H. pluvialis in locations confronted by hot summer weather, particularly in large-scale closed photobioreactor systems. [ABSTRACT FROM AUTHOR]

Haematococcus pluvialis is the richest source of natural astaxanthin (3S, 3′S), but the rigid cell wall of mature red cyst (aplanospore) complicates the efficient extraction of astaxanthin from the strain. Herein, the cyst germination method was developed by using nitrate and light for practical application for an efficient astaxanthin extraction from Haematococcus cells cultured in outdoor condition where flue gas, solar radiation and photobioreactor were used. Notably, autotrophic germination rate was easily regulated by light intensity. Under conditions of low germination rate, total astaxanthin concentration was highly maintained and astaxanthin extraction efficiency was rapidly enhanced during autotrophic germination. As a result, under homogenization (30 s), the extracted astaxanthin concentration in the cells treated with 1 mM KNO 3 –150 μE/m 2 /s was highly increased by 58% compared to the cells treated without germination. Our technical solution will definitely improve an astaxanthin extraction titer with the practical application in outdoor Haematococcus culture system. [ABSTRACT FROM AUTHOR]

Carbon dioxide sequestration by microalgae photosynthesis is an attractive alternative to mitigate climate change due to greenhouse gas emission. In our study, Haematococcus pluvialis and a sequential operating system were exploited to examine the carbon dioxide fixation efficiency in a tubular photobioreactor. We investigated the carbon balance over the photobioreactor, including the carbon bound in the biomass, dissolved inorganic carbon in the liquid media, and gaseous carbon remained in the headspace and vented out from the photobioreactor. The experiments were performed both indoors and outdoors, using air-mixed 3% CO 2 gas and the flue gas from power plant. As a result, the sequential operation system using H. pluvialis cultivation improved the carbon dioxide fixation efficiencies from 12.34% to 49.37% (indoor), and from 13.55% to 49.15% (outdoor), respectively, compared to single bioreactor operation mode. This sequential operating system would be useful for enhanced conversion of carbon dioxide from flue gas by microalgae photosynthesis. [ABSTRACT FROM AUTHOR]

High temperatures (30-36 °C) inhibited astaxanthin accumulation in Haematococcus pluvialis under photoautotrophic conditions. The depression of carotenogenesis was primarily attributed to excess intracellular less reactive oxygen species (LROS; O and HO) levels generated under high temperature conditions. Here, we show that the heat stress-driven inefficient astaxanthin production was improved by accelerating the iron-catalyzed Haber-Weiss reaction to convert LROS into more reactive oxygen species (MROS; O and OH·), thereby facilitating lipid peroxidation. As a result, during 18 days of photoautotrophic induction, the astaxanthin concentration of cells cultured in high temperatures in the presence of iron (450 μM) was dramatically increased by 75 % (30 °C) and 133 % (36 °C) compared to that of cells exposed to heat stress alone. The heat stress-driven Haber-Weiss reaction will be useful for economically producing astaxanthin by reducing energy cost and enhancing photoautotrophic astaxanthin production, particularly outdoors utilizing natural solar radiation including heat and light for photo-induction of H. pluvialis. [ABSTRACT FROM AUTHOR]

Abstract: Haematococcus pluvialis synthesizes a high yield of astaxanthin using CO2 in a photoautotrophic culture without contaminant heterotrophs; however, it takes too long to induce astaxanthin production. In this study, a highly photosensitive mutant strain was attained by conventional random mutagenesis and an efficient isolation method to shorten induction time. Sensitivity to photoinhibition in this mutant was raised by a partial lesion in the photosystem II (PSII) of photosynthesis, thereby prompting a change in cellular morphology as well as stimulating carotenogenesis (astaxanthin production). As a result, the concentrations of cell biomass and astaxanthin were dramatically increased by 27% and 62% under strong light and 79% and 153% under moderate light, respectively. This Haematococcus mutant would be useful for the economical astaxanthin production capable of reducing the light energy cost in a photoautotrophic culture system, even in areas with insufficient sunlight. [Copyright &y& Elsevier]

Abstract: The economic production of biofuels from renewable biomass using Saccharomyces cerevisiae requires tolerance to high concentrations of sugar and alcohol. Here we applied an inverse metabolic engineering approach to identify endogenous gene targets conferring improved alcohol tolerance in S. cerevisiae. After transformation with a S. cerevisiae genomic library, enrichment of the transformants exhibiting improved tolerance was performed by serial subculture in the presence of iso-butanol (1%). Through sequence analysis of the isolated plasmids from the selected transformants, four endogenous S. cerevisiae genes were identified as overexpression targets eliciting improved tolerance to both iso-butanol and ethanol. Overexpression of INO1, DOG1, HAL1 or a truncated form of MSN2 resulted in remarkably increased tolerance to high concentrations of iso-butanol and ethanol. Overexpression of INO1 elicited the highest ethanol tolerance, resulting in higher titers and volumetric productivities in the fermentation experiments performed with high glucose concentrations. In addition, the INO1-overexpressing strain showed a threefold increase in the specific growth rate as compared to that of the control strain under conditions of high levels of glucose (10%) and ethanol (5%). Although alcohol tolerance in yeast is a complex trait affected by simultaneous interactions of many genes, our results using a genomic library reveal potential target genes for better understanding and possible engineering of metabolic pathways underlying alcohol tolerance phenotypes. [ABSTRACT FROM AUTHOR]

[Display omitted] • Repeated sequential auto-and heterotrophic (RSAH) culture mode improves biomass productivity. • RSAH shows effective conversion of organic carbon source to biomass. • TCA cycle of RSAH mode is more active compared to mixotrophic mode. • RSAH is promising for carbon reduction and economic feasibility. A repeated sequential auto-and heterotrophic (RSAH) culture mode was designed to enhance biomass of Chlorella protothecoides. Based on the result that the photosynthesis system may receive damage if the light period is more than 16 h, autotrophy was applied in the 16 h of the light cycle and mixotrophy using acetic acid and glucose in the 8 h of dark cycle. In the dark cycle, an organic carbon source was added according to the Monod equation to maintain activation of the TCA cycle and organic carbon source-to-cell conversion. When acetic acid and glucose were used as organic carbon sources, this culture method was found to be 32.3% and 12.6% higher in biomass, 2.59 and 2.67 times higher in the organic carbon source-to-cell conversion factor, and 2.17 and 2.32 times higher in ATP/ADP ratio, respectively, compared to mixotrophy. Through this new culture method, economic feasibility and carbon reduction capabilities in large-scale cultures can be achieved. [ABSTRACT FROM AUTHOR]

[Display omitted] • Green decontamination tool was created to eliminate predators cidal to H. pluvialis. • CBDS was conducted at mild alkalinity and low CaCl 2 for non-calcifying H. pluvialis. • CBDS showed an efficient removal of algicidal bacteria and fungi during cultivation. • Astaxanthin production using CBDS was significantly enhanced in H. pluvialis. • Large-scale outdoor astaxanthin production in H. pluvialis was improved by CBDS. Currently, there is a lack of an efficient, environmentally-benign and sustainable industrial decontamination strategy to steadily achieve improved astaxanthin production from Haematococcus pluvialis under large-scale outdoor conditions. Here, this study demonstrates for the first time that a CaCO 3 biomineralization-based decontamination strategy (CBDS) is highly efficient in selectively eliminating algicidal microorganisms, such as bacteria and fungi, during large-scale H. pluvialis cultivation under autotrophic and mixotrophic conditions, thereby augmenting the astaxanthin productivity. Under outdoor AT and MT conditions, the average astaxanthin productivity of H. pluvialis using CBDS in a closed photobioreactor system was substantially increased by 14.85- (1.19 mg L−1 d−1) and 13.65-fold (2.43 mg L−1 d−1), respectively, compared to the contaminated H. pluvialis cultures. Given the exponentially increasing demand of astaxanthin, a natural anti-viral, anti-inflammatory, and antioxidant drug, CBDS will be a technology of interest in H. pluvialis -based commercial astaxanthin production which has been hindered by the serious biological contaminations. [ABSTRACT FROM AUTHOR]

• 10 mM Ca2+ improved coincident production of biomass/lipid (PUFA) in C. sorokiniana. • Microalgal ω-3 was highly enhanced at 23 °C via Ca2+-induced homeoviscous adaptation. • Lipid productivity was maximally increased when Ca2+-based 1-strategy was recycled. This study aimed to improve valuable omega-3 fatty acids production in freshwater microalgae at normal temperature by inducing homeoviscous adaptation using CaCl 2 , which could have a role in decreasing the cellular membrane fluidity followed by increasing the rigidity of cell wall and membranes. At 10 mM CaCl 2 , simultaneous biomass and lipid production was obtained by Ca2+-based single strategy without considerable sacrifice of cellular logarithmic growth in Chlorella sorokiniana. The cells cultured at 10 mM CaCl 2 (1-stage) showed relatively high levels of cellular membrane fluidity, caused by increased content in unsaturated fatty acids, compared to the conventional culture strategy (2-stage). Moreover, when this process was recycled by repeated-batch fermentation, the EPA productivity of 1-stage was 4.338 mg L−1 d−1, conspicuously increased by over 1300% compared to 2-stage. This strategy enhances the valuable omega-3 production, which can be commercially used for mass cultivation of omega-3-enriched biomass in the microalgae industry. [ABSTRACT FROM AUTHOR]

• CaCO 3 crystal(CN)-coating much improve the microalgal biomass and lipid production. • CN-coating is carried out at mild alkali pH, CaCl 2 under N-starvation in microalgae. • Autotroph Neochloris show superior CaCO 3 crystallization after 6 days of induction. • Photosynthesis is augmented by anisotropic CN-driven light splitting at high light. • Separated biogenic CaCO 3 crystal could be highly beneficial in microalgal industry. The aim of this work was to study the anisotropic effect of crystalline CaCO 3 nanoparticles (CN)-driven multiple refraction/scattering from the CN-coated agglomerated cells on the rate of photosynthesis and the product yield under high light conditions in the freshwater microalgae Neochloris oleoabundans. The CN-coating via biomineralization significantly improved the biomass and lipid production of N. oleoabundans during second stage of autotrophic induction by sustaining relatively high rate of photosynthesis at high irradiance using the multiple-splitting effect of the anisotropic polymorphism. The CN were successfully produced, adsorbed and grown on the external cells under conditions of mild alkalinity (pH 7.5–8.0), mild CaCl 2 concentration (0.05 M) and under nitrogen starvation with strong light (400 µE m−2 s−1). Consequently, lipid content and productivity of N. oleoabundans cells cultured with 0.05 M CaCl 2 increased by 18.4% and 31.5%, respectively, compared to the cells cultured with 0.05 M CaCl 2 and acetazolamide to inhibit calcification. [ABSTRACT FROM AUTHOR]

The combinatorial approach of anthropogenic activities and CO2 sequestration is becoming a global research trend to alleviate the average global temperature. Although microalgae have been widely used to capture CO2 from industrial flue gas, the application of bioproducts was limited to bioenergy due to the controversy over the quality and safety of the products in the food and feed industry. Herein, the waste CO2 emitted from large point sources was directly captured using astaxanthin-hyperproducing microalgae Haematococcus pluvialis. Astaxanthin production was successfully carried out using the hypochlorous acid water-based axenic culture process under highly contamination-prone outdoor conditions. Consequently, after 36 days of autotrophic induction, the productivity of biomass and astaxanthin of H. pluvialis (the mutant) reached 0.127 g L−1 day−1 and 5.47 mg L−1 day−1 under high summer temperatures, respectively, which was 38% and 48% higher than that of wild type cell. After grinding the wet astaxanthin-enriched biomass, the extract was successfully approved by compliance validation testing from Korea Food and Drug Administration. The assorted feed improved an immune system of the poultry without causing any side effects. The flue gas-based bioproducts could certainly be used for health functional food for animals in the future. [ABSTRACT FROM AUTHOR]

Highlights • Light irradiance exhibited variability in growth response based on substrate types. • Each substrate exhibited variability of light requirement for mixotrophic growth. • Continuous light-deficient condition was adequate for effective mixotrophy from glucose. • Acetic acid exhibited better mixotrophic yield at light-sufficient condition. • Variability in photosynthetic-efficiency in mixotrophy dependent on substrate types. Abstract Current research aimed to increase mixotrophic biomass from various organic carbon sources by exploring best light conditions. Three substrates glucose, acetic acid and glycerol were studied for their effects on mixotrophic microalgae cultivation under four light conditions. Light irradiance exhibited variability in growth response and photosynthetic efficiency based on type of substrates used in mixotrophic growth. Each substrate showed variability in light requirements for their effective assimilations. From growth responses, glucose and acetic acid respectively exhibited heterotrophic and mixotrophic (better growth in light) natures. Continuous light-deficient condition was adequate for effective mixotrophic growth as well as energy saving for glucose. However, light-sufficient condition required for effective acetic acid supported mixotrophic growth. Mixotrophic benefits from glycerol and its uptake by Chlorella protothecoides was negligible in all light conditions. Investigation of heterotrophic biomass contribution by various substrates in overall mixotrophic yield, glucose offered maximum approx. 43% contribution. [ABSTRACT FROM AUTHOR]

The aim of this work was to develop a high efficient photobioreactor for increasing biomass and lipid production in microalgae by assessment of the hydrodynamic properties and k L a which are important parameters for improving the algal cultivation efficiency. We designed three different photobioreactors (H-Shape, X-Shape and serial-column). Among them, X-Shape showed the highest hydrodynamic properties and k L a for algal cultivation. Thus, we evaluated the biomass and the lipid production in a 20 L scale-up X-Shape photobioreactor. The biomass and lipid production from X-Shape photobioreactor are 1.359 ± 0.007 g L −1 and 117.624 ± 3.522 mg L −1 , respectively; which are 30.05% and 23.49% higher than those from the control photobioreactor. Finally, we observed the lipid from X-Shape had high MUFAs, CN and low IV, which is suitable for high quality of biodiesel, suggesting that it can be practicably utilized for mass production of algal biofuel. [ABSTRACT FROM AUTHOR]

In the era of targeted therapy, mutation profiling of cancer is a crucial aspect of making therapeutic decisions. To characterize cancer at a molecular level, the use of formalin-fixed paraffin-embedded tissue is important. We tested the Ion AmpliSeq Cancer Hotspot Panel v2 and nCounter Copy Number Variation Assay in 89 formalin-fixed paraffin-embedded gastric cancer samples to determine whether they are applicable in archival clinical samples for personalized targeted therapies. We validated the results with Sanger sequencing, real-time quantitative PCR, fluorescence in situ hybridization and immunohistochemistry. Frequently detected somatic mutations included TP53 (28.17%), APC (10.1%), PIK3CA (5.6%), KRAS (4.5%), SMO (3.4%), STK11 (3.4%), CDKN2A (3.4%) and SMAD4 (3.4%). Amplifications of HER2, CCNE1, MYC, KRAS and EGFR genes were observed in 8 (8.9%), 4 (4.5%), 2 (2.2%), 1 (1.1%) and 1 (1.1%) cases, respectively. In the cases with amplification, fluorescence in situ hybridization for HER2 verified gene amplification and immunohistochemistry for HER2, EGFR and CCNE1 verified the overexpression of proteins in tumor cells. In conclusion, we successfully performed semiconductor-based sequencing and nCounter copy number variation analyses in formalin-fixed paraffin-embedded gastric cancer samples. High-throughput screening in archival clinical samples enables faster, more accurate and cost-effective detection of hotspot mutations or amplification in genes. [ABSTRACT FROM AUTHOR]

Microalgae can rapidly sequester carbon dioxide (CO 2) and convert it into various marketable products. Thus, these photosynthetic microorganisms have gained substantial attention as prospective biological platforms for the practical reduction of CO 2 and establishing renewable and sustainable supply chains. However, conventional biomass applications to which attention has been directed, such as a feedstock for biodiesel production, are only achievable through cumbersome downstream processes, including extraction, fractionation, separation, and refinement. These stereotypical biomass utilization strategies have increased concerns regarding economic, energetic, and environmental viability. As a promising alternative, utilization of whole microalgal biomass as end-products has emerged because it can directly provide various beneficial commodities through a streamlined production route only consisting of harvesting and drying processes. The process review in this study clearly shows the energy and CO 2 reduction efficiencies of this strategy compared with other traditional production routes. Despite the high potential, this application strategy has been overlooked because of the limited commercialized examples and the broad use of established methods. Recently, many applications have been suggested, and their practicality has been thoroughly verified according to the main biochemical constituents, namely carbohydrates, proteins, and lipids. Raw microalgal biomass produced by a potentially carbon-negative and net-energy-positive process can be employed as-is in an extensive range of fields that cover most human needs, including nutritious foods and feeds with bioactive functions, cosmetics, thermoplastic materials, and fuels for direct combustion. Thus, this comprehensive review aims to provide an opportunity to reconsider the potential and practicality of whole microalgal biomass utilization strategies. [Display omitted] • The advantages of a whole microalgal biomass utilization strategy are discussed. • The strategy provides various products with energetic and environmental benefits. • Carbohydrate-rich microalgae can be used as foods, cosmetics, and materials. • Proteinaceous microalgae can be utilized as nutraceuticals, fodders, and bioplastics. • Oleaginous microalgae can be exploited as solid fuels, functional foods, and feeds. [ABSTRACT FROM AUTHOR]

Microalgae-derived biomass is currently considered a sustainable feedstock for making biofuels, including biodiesel and direct combustion fuel. The photoautotrophic cultivation of microalgae using flue gas from power plants has been continuously investigated to improve the economic feasibility of microalgae processes. The utilization of waste CO2 from power plants is advantageous in reducing carbon footprints and the cost of carbon sources. Nonetheless, the sudden interruption of CO2 supply during microalgal cultivation leads to a severe reduction in biomass productivity. Herein, chemical fertilizers including urea and KH2PO4 were added to the culture medium when CO2 supply was halted. Urea (5 mM) and KH2PO4 (5 mM) were present in the culture medium in the form of CO2/NH4+ and K+/H2PO4−, respectively, preventing cell growth inhibition. The culture with urea and KH2PO4 supplementation exhibited 10.02-fold higher and 7.28-fold higher biomass and lipid productivity, respectively, compared to the culture with ambient CO2 supply due to the maintenance of a stable pH and dissolved inorganic carbon in the medium. In the mass cultivation of microalgae using flue gas from coal-fired power plants, urea and KH2PO4 were supplied while the flue gas supply was shut off. Consequently, the microalgae were grown successfully without cell death. [ABSTRACT FROM AUTHOR]

• Split mixotrophy cultivation strategy (SMCS) improves growth conditions and lipid yields. • SMCS exhibited better energy recovery than the common mixotrophy. • SMCS solves the mixotrophic associated challenges like Chl reduction by glucose. • SMCS is promising for integrating dissimilar bioprocesses and cost-effectiveness. • SMCS exhibit rather more robust system than common mixotrophic cultivation. • Graphical abstact. Mixotrophy (M) assumes sum of autotrophic (A) and heterotrophic (H) growths. In this study, a novel split-mixotrophic cultivation strategy (SMCS) developed as better mixotrophy via offering mutual-benefits through gas-exchange at both headspaces while splitting both trophic modes. To quantify synergistic-growth effects in combined-autotrophy and combined-heterotrophy (CA&CH) of SMCS, gross O 2 -evolution, DIC and DO concentrations were compared with A, H and M. Average 12–14% and 26–32% increase in DIC and DO concentrations were determined respectively in CA and CH than A, H and M. Biomass yield in CA + CH was increased approx.1.5-folds higher than yields of A + H and M regimes. These results show SMCS as better cultivation strategy than the M by increased biomass and lipid yields. Challenges associated with organic carbon can be solved by SMCS viz. chlorophyll loss, organic carbon uptake inhibition. SMCS could be a breakthrough to integrate bacterial process with algae for better bioprocess economy and energy recovery. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Comparison of imidazolium ionic liquids (ILs) for disruption of H. pluvialis cyst. • Co-extraction of lipid and astaxanthin using room-temperature IL/water mixtures. • Very high astaxanthin recoveries (>99%) by IL pretreatments and hexane extractions. Abstract Energy-saving, high-efficiency cell disruption is a critical step for recovery of thermolabile antioxidant astaxanthin from Haematococcus pluvialis cyst cells of rigid cell-wall structure. In this study, as room-temperature green solvents, 10 types of 1-ethyl-3-methylimidazolium ([Emim])-based ionic liquids (ILs) were compared and evaluated for their abilities to disrupt H. pluvialis cyst cells for astaxanthin/lipid extraction. Among the 10 ILs tested, 3 [Emim]-based ILs with HSO 4 , CH 3 SO 3 , and (CF 3 SO 2) 2 N anions were selected based on astaxanthin/lipid extraction performance and synthesis cost. When pretreated with IL/water mixtures, intact cyst cells were significantly torn, broken or shown to release cytoplasmic components, thereby facilitating subsequent separation of astaxanthin/lipid by hexane. However, excess IL pretreatments at high temperature/IL dosages and longer incubation times significantly deteriorated lipid and/or astaxanthin. Under optimized mild conditions (6.7% (v/v) IL in water solution, 30 °C, 60 min), almost complete astaxanthin recoveries (>99%) along with moderate lipid extractions (∼82%) could be obtained. [ABSTRACT FROM AUTHOR]

Highlights • Direct combustion realizes the full potential energy yield from microalgal biomass. • Microalgae's oleaginous property contributes to their high calorific values. • Their high carbon content increases the energy density and CO 2 reduction effects. • Synergistic effects of coal-microalgae co-firing were quantitatively confirmed. • The solid fuel shows better performance than woody biomass in various properties. Abstract Direct combustion of biomass is considered the most effective and simple means to contribute to CO 2 reduction. In this context, the life-cycle potential of microalgal solid fuel, which has been overlooked so far, was comprehensively scrutinized ranging from cultivation to direct combustion. According to the quantitative data, using the raw fuel was confirmed to offer great benefits over the conventional lipid-targeted microalgal fuel systems through exploiting all of the biomass' energy potential, thereby being able to significantly increase the energy yield from biomass. The solid fuel is shown to exhibit diverse positive aspects owing to its remarkable calorific value, productivity and CO 2 fixation ability. The combustion test reveals coal-microalgae co-combustion brings beneficial consequences on combustibility and environmental impacts with no notable thermal efficiency drop. This holistic appraisal shows microalgae patently possess high potential as a direct combustion fuel, even outperforming that of extensively used woody fuels. [ABSTRACT FROM AUTHOR]

The aim of this study was to develop the economic and effective buffer system for microalgae mass cultivation using industrial flue gas. Due to the continuous flue gas supplement, culture media acidified, therefore cell growth inhibited. Although buffering agent was added, this result increase in cost for overall culture process. Therefore combined buffer system of bicarbonate and phosphate (BP) for large-scale use was investigated. The bicarbonate buffer system generated from CO 2 dissolution, additionally phosphate buffer system improves the buffer performance under the continuous CO 2 supplementation from flue gas. The microalgae Haematococcus pluvialis was cultivated under autotrophic outdoor conditions using these buffer solutions. As a result, the autotrophic BP buffer system enhanced the biomass and astaxanthin productivity of H. pluvialis to 105% and 103%, respectively. The results confirm that the BP buffer system reduces the cost of microalgal CO 2 conversion process, particularly for the outdoor mass cultivation. [ABSTRACT FROM AUTHOR]