Microalgae are not an umbrella solution for power industry waste abatement but could play a role in their valorization

Microalgae have long been regarded as a promising solution for biological carbon abatement from the power industry, offering renewable biomass without competing for land or water resources used for food crops. In this study, we extensively examined the application of photosynthetic microorganisms for closing carbon, nitrogen, and micronutrient loops in the power industry. Subsequently, we explored the bottom-up integration of algal biorefineries into power industry waste streams for increased economic benefits and reduced environmental impacts. Analysis of the available data indicated that microalgae integration with the power industry is primarily performed using flue-gas-assisted cultivation. This approach allows for carbon sequestration typically below one gram per liter per day, too low to significantly impact carbon abatement at achievable scales of microalgae cultivation. Alternative approaches are also being explored. For example, soluble bicarbonate platforms allow for higher biomass productivity and temporary carbon storage. Meanwhile, the use of ashes and waste heat and thermophilic strains can result in lower cultivation costs and better control of cultivation conditions. These approaches offer further incremental improvement to microalgae-based carbon abatement systems in the power industry but are unlikely to be an umbrella solution for carbon reduction. Consequently, in the near term, microalgae-based carbon valorization systems are likely to be limited to niche applications involving the synthesis of high-value products. For microalgae to truly transform carbon abatement processes radical improvements in both biology and engineering approaches are urgently needed.

Microalgal lutein: Advancements in production, extraction, market potential, and applications

Lutein, a bioactive xanthophyll, has recently attracted significant attention for numerous health benefits, e.g., protection of eye health, macular degeneration, and acute and chronic syndromes etc. Microalgae have emerged as the best platform for high-value lutein production with high productivity, lutein content, and scale-up potential. Algal lutein possesses numerous bioactivities, hence widely used in pharmaceuticals, nutraceuticals, aquaculture, cosmetics, etc. This review highlights advances in upstream lutein production enhancement and feasible downstream extraction and cell disruption techniques for a large-scale lutein biorefinery. Besides bioprocess-related advances, possible solutions for existing production challenges in microalgae-based lutein biorefinery, market potential, and emerging commercial scopes of lutein and its potential health applications are also discussed. The key enzymes involved in the lutein biosynthesizing Methyl-Erythritol-phosphate (MEP) pathway have been briefly described. This review provides a comprehensive updates on lutein research advancements covering scalable upstream and downstream production strategies and potential applications for researchers and industrialists.

A Low-Cost Fertilizer Medium Supplemented with Urea for the Lutein Production of Chlorella sp. and the Ability of the Lutein to Protect Cells against Blue Light Irradiation

This study aimed to investigate the use of organic fertilizers instead of modified f/2 medium for Chlorella sp. cultivation, and the extracted lutein of the microalga to protect mammal cells against blue-light irradiation. The biomass productivity and lutein content of Chlorella sp. cultured in 20 g/L fertilizer medium for 6 days were 1.04 g/L/d and 4.41 mg/g, respectively. These values are approximately 1.3- and 1.4-fold higher than those achieved with the modified f/2 medium, respectively. The cost of medium per gram of microalgal biomass reduced by about 97%. The microalgal lutein content was further increased to 6.03 mg/g in 20 g/L fertilizer medium when supplemented with 20 mM urea, and the cost of medium per gram lutein reduced by about 96%. When doses of ≥1 μM microalgal lutein were used to protect mammal NIH/3T3 cells, there was a significant reduction in the levels of reactive oxygen species (ROS) produced by the cells in the following blue-light irradiation treatments. The results show that microalgal lutein produced by fertilizers with urea supplements has the potential to develop anti-blue-light oxidation products and reduce the economic challenges of microalgal biomass applied to carbon biofixation and biofuel production.

Lutein production from microalgae: A review

Lutein production from microalgae is a sustainable and economical strategy to offer the increasing global demands, but is still challenged with low lutein content at the high-cell density for commercial production. This review summarizes the suitable conditions for cell growth and lutein accumulation, and presents recent cultivation strategies to further improve lutein productivity. Light and nitrogen play critical roles in lutein biosynthesis that lead to the efficient multi-stage cultivation by increasing lutein content at the later stage. In addition, metabolic and genetic designs for carbon regulation and lutein biosynthesis are discussed at the molecule level. The in-situ lutein accumulation in fermenters by regulating carbon metabolism is considered as a cost-effective direction. Then, downstream processes are summarized for the efficient lutein recovery. Finally, challenges of current lutein production from microalgae are discussed. Meanwhile, potential solutions are proposed to improve lutein content and drive down costs of microalgal biomass.

A Two-Stage Culture Strategy for Scenedesmus sp. FSP3 for CO2 Fixation and the Simultaneous Production of Lutein under Light and Salt Stress

In this study, Scenedesmus sp. FSP3 was cultured using a two-stage culture strategy for CO₂ fixation and lutein production. During the first stage, propylene carbonate was added to the medium, with 5% CO₂ introduced to promote the rapid growth and CO₂ fixation of the microalgae. During the second stage of cultivation, a NaCl concentration of 156 mmol L^-1 and a light intensity of 160 μmol m^-2 s^-1 were used to stimulate the accumulation of lutein in the microalgal cells. By using this culture method, high lutein production and CO₂ fixation were simultaneously achieved. The biomass productivity and carbon fixation rate of Scenedesmus sp. FSP3 reached 0.58 g L^-1 d^-1 and 1.09 g L^-1 d^-1, with a lutein content and yield as high as 6.45 mg g^-1 and 2.30 mg L^-1 d^-1, respectively. The results reveal a commercially feasible way to integrate microalgal lutein production with CO₂ fixation processes.

A Two-Stage Culture Strategy for Scenedesmus sp. FSP3 for CO2 Fixation and the Simultaneous Production of Lutein under Light and Salt Stress

In this study, Scenedesmus sp. FSP3 was cultured using a two-stage culture strategy for CO2 fixation and lutein production. During the first stage, propylene carbonate was added to the medium, with 5% CO2 introduced to promote the rapid growth and CO2 fixation of the microalgae. During the second stage of cultivation, a NaCl concentration of 156 mmol L-1 and a light intensity of 160 μmol m-2 s-1 were used to stimulate the accumulation of lutein in the microalgal cells. By using this culture method, high lutein production and CO2 fixation were simultaneously achieved. The biomass productivity and carbon fixation rate of Scenedesmus sp. FSP3 reached 0.58 g L-1 d-1 and 1.09 g L-1 d-1, with a lutein content and yield as high as 6.45 mg g-1 and 2.30 mg L-1 d-1, respectively. The results reveal a commercially feasible way to integrate microalgal lutein production with CO2 fixation processes.

Rapid green microwave assisted extraction of lutein from Chlorella sorokiniana (NIOT-2) - Process optimization

Chloropycean microalgae are looked up as a prospective alternate source for the production of xanthophyll carotenoid lutein. Despite, the market significance and multitude of nutraceutical applications of lutein commercial production from microalgae still remains a challenge due to the prohibitive downstream cost. This necessitates innovative less energy intensive, high lutein yielding green processes. The present work presents a comprehensive study on the rapid green microwave assisted extraction (MAE) of lutein from marine chlorophycean microalgae Chlorella sorokiniana (NIOT-2). The process parameters of microwave assisted alkali pre-treatment like exposure time (ET), alkali concentration (AC) and solid (biomass): liquid (aqueous Potassium hydroxide-KOH) ratio (S: L ratio) were optimized using single factor and response surface method (RSM) experiments. The optimized conditions for microwave assisted alkali pre-treatment (ET:1.47 min; AC: 8.16 M KOH and S:L ratio of 36.8:1 (mg/mL) augmented the lutein yield (20.69 ± 1.2 mg/g) 3.26 fold when compared to conventional extraction (6.35 ± 0.44 mg/g). Lutein extracted using optimized MAE conditions was purified and characterized. Visualization of the MAE extracted algal biomass using Scanning electron microscope confirmed the effective cell disruption. X-ray diffraction (XRD) analysis of microwave assisted alkali treated biomass (83.85%) revealed a significantly higher crystallinity index when compared to untreated control (17.28%). MAE pre-treatment can thus be propounded as a suitable process for lutein extraction from marine microalgae due to its amalgamated rapidity, homogenous heating, less energy intensiveness and high extraction yield.

Developing a Chromochloris zofingiensis Mutant for Enhanced Production of Lutein under CO2 Aeration

Microalgae are competitive and commercial sources for health-benefit carotenoids. In this study, a Chromochloris zofingiensis mutant (Cz-pkg), which does not shut off its photosystem and stays green upon glucose treatment, was generated and characterized. Cz-pkg was developed by treating the algal cells with a chemical mutagen as N-methyl-N’-nitro-N-nitrosoguanidine and followed by a color-based colony screening approach. Cz-pkg was found to contain a dysfunctional cGMP-dependent protein kinase (PKG). By cultivated with CO₂ aeration under mixotrophy, the mutant accumulated lutein up to 31.93 ± 1.91 mg L⁻¹ with a productivity of 10.57 ± 0.73 mg L⁻¹ day⁻¹, which were about 2.5- and 8.5-fold of its mother strain. Besides, the lutein content of Cz-pkg could reach 7.73 ± 0.52 mg g⁻¹ of dry weight, which is much higher than that of marigold flower, the most common commercial source of lutein. Transcriptomic analysis revealed that in the mutant Cz-pkg, most of the genes involved in the biosynthesis of lutein and chlorophylls were not down-regulated upon glucose addition, suggesting that PKG may regulate the metabolisms of photosynthetic pigments. This study demonstrated that Cz-pkg could serve as a promising strain for both lutein production and glucose sensing study.

A novel flat-panel photobioreactor for simultaneous production of lutein and carbon sequestration by Chlorella sorokiniana TH01

Carbon dioxide is the major cause of global warming. However, it is a carbon source for phototrophic production of chemicals from microalgae. In this work, a novel flat-panel photobioreactor (FPP) was used for maximization of biomass and lutein production and CO₂ fixation by a lutein-rich C. sorokiniana TH01. CO₂ concentration, light intensity and aeration rate were optimized as 5%, 150 µmol/m²/s and 1 L/min, respectively. The highest biomass productivity, lutein productivity and CO₂ fixation efficiency were measured for indoor single and sequential FPPs were 284 - 469 mg/L/d, 2.57 - 4.57 mg/L/d, and 63 - 100%, respectively. In a climatic condition of 25.5 - 33 °C and 86 - 600 µmol/m²/s, C. sorokiniana TH01 achieved lutein productivity and CO₂ fixation efficiency of 2.1 - 3.03 mg/L/d and 56 - 81%, respectively, while the comparable biomass productivity of 284 - 419 mg/L/d was maintained. This pioneered FPP system was efficiently demonstrated for production of algal lutein from CO₂.

Challenges in microalgal biofuel production: A perspective on techno economic feasibility under biorefinery stratagem

Rapidly exhausting fossil fuels combined with the ever-increasing demand for energy led to an ongoing search for alternative energy sources to meet the transportation, manufacturing, domestic and other energy demands of the grown population. Microalgae are at the forefront of alternative energy research due to their significant potential as a renewable feedstock for biofuels. However, microalgae platforms have not found a way into industrial-scale bioenergy production due to various technical and economic constraints. The present review provides a detailed overview of the challenges in microalgae production processes for bioenergy purposes with supporting techno-economic assessments related to microalgae cultivation, harvesting and downstream processes required for crude oil or biofuel production. In addition, biorefinery approaches that can valorize the by-products or co-products in microalgae production and enhance the techno-economics of the production process are discussed.

Microalgae for high-value products: A way towards green nutraceutical and pharmaceutical compounds

Microalgae is a renewable bioresource with the potential to replace the conventional fossil-based industrial production of organic chemicals and pharmaceuticals. Moreover, the microalgal biomass contains carotenoids, vitamins, and other biomolecules that are widely used as food supplements. However, the microalgal biomass production, their composition variations, energy-intensive harvesting methods, optimized bio-refinery routes, and lack of techno-economic analysis are the major bottleneck for the life-sized commercialization of this nascent bio-industry. This review discusses the microalgae-derived key bioactive compounds and their applications in different sectors for human health. Furthermore, this review proposes advanced strategies to enhance the productivity of bioactive compounds and highlight the key challenges associated with a safety issue for use of microalgae biomass. It also provides a detailed global scenario and market demand of microalgal bioproducts. In conclusion, this review will provide the concept of microalgal biorefinery to produce bioactive compounds at industrial scale platform for their application in the nutraceutical and pharmaceutical sector considering their current and future market trends.

Optimization of Chlamydomonas reinhardtii cultivation with simultaneous CO2 sequestration and biofuels production in a biorefinery framework

Algal biomass is regarded as a sustainable energy feedstock for the future. Enhancement of the biomass and metabolite production of microalgae increases the economic feasibility of the biofuel production process. The present study encompasses on bioethanol production from Chlamydomonas reinhardtii through a biorefinery approach. The biomass and carbohydrate productivity of C. reinhardtii UTEX 90 and CC 2656 were enhanced by optimizing the physico-chemical parameters. The following conditions were found suitable for the improvement of biomass and metabolite content of C. reinhardtii: pH 6.5-7.0, incubation temperature 30 °C, initial acetate and ammonium chloride concentration of 1.56 g L^-1 and 100-200 mg L^-1, respectively. Under the optimized operational condition biomass and carbohydrate productivity of C. reinhardtii UTEX 90 and CC 2656 were 512 mg L^-1 d^-1 & 266.24 mg L^-1 d^-1 and 364 mg L^-1 d ^-1 & 163.80 mg L^-1 d^-1, respectively. The amount of CO₂ sequestered during the cultivation process by UTEX 90 and CC 2656 were 113 mg L^-1 d^-1 and 74.95 mg L^-1 d^-1, respectively. The depigmented and defatted carbohydrate rich biomass was considered as raw material for bioethanol production. The bioethanol yield range was 90-94% of the theoretical yield using Saccharomyces cerevisiae INVSC-1 in a double jacket reactor. To improve the viability of the process, the spent media after ethanol fermentation was subsequently used for methane production using mixed microbial consortium. The energy recovery from the process was 40.39% and 39.7% for UTEX 90 and CC 2656, respectively when C. reinhardtii biomass was used as substrate for biofuel production. The present investigation concedes with the potentiality of algae as a favourable 3rd generation feedstock to address the existing challenges of clean energy production with concomitant CO₂ sequestration.

Microalgae with artificial intelligence: A digitalized perspective on genetics, systems and products

With recent advances in novel gene-editing tools such as RNAi, ZFNs, TALENs, and CRISPR-Cas9, the possibility of altering microalgae toward designed properties for various application is becoming a reality. Alteration of microalgae genomes can modify metabolic pathways to give elevated yields in lipids, biomass, and other components. The potential of such genetically optimized microalgae can give a "domino effect" in further providing optimization leverages down the supply chain, in aspects such as cultivation, processing, system design, process integration, and revolutionary products. However, the current level of understanding the functional information of various microalgae gene sequences is still primitive and insufficient as microalgae genome sequences are long and complex. From this perspective, this work proposes to link up this knowledge gap between microalgae genetic information and optimized bioproducts using Artificial Intelligence (AI). With the recent acceleration of AI research, large and complex data from microalgae research can be properly analyzed by combining the cutting-edge of both fields. In this work, the most suitable class of AI algorithms (such as active learning, semi-supervised learning, and meta-learning) are discussed for different cases of microalgae applications. This work concisely reviews the current state of the research milestones and highlight some of the state-of-art that has been carried out, providing insightful future pathways. The utilization of AI algorithms in microalgae cultivation, system optimization, and other aspects of the supply chain is also discussed. This work opens the pathway to a digitalized future for microalgae research and applications.

Enhancing Biomass and Lutein Production From Scenedesmus almeriensis: Effect of Carbon Dioxide Concentration and Culture Medium Reuse

The main purpose of this study is to investigate the effects of operative parameters and bioprocess strategies on the photo-autotrophic cultivation of the microalgae Scenedesmus almeriensis for lutein production. S. almeriensis was cultivated in a vertical bubble column photobioreactor (VBC-PBR) in batch mode and the bioactive compounds were extracted by accelerated solvent extraction with ethanol at 67°C and 10 MPa. The cultivation with a volume fraction of CO₂ in the range 0-3.0%v/v showed that the highest biomass and lutein concentrations - 3.7 g/L and 5.71 mg/g, respectively - were measured at the highest CO₂ concentration and using fresh growth medium. Recycling the cultivation medium from harvested microalgae resulted in decreased biomass and lutein content. The nutrient chemical composition analysis showed the highest consumption rates for nitrogen and phosphorus, with values higher than 80%, while sulfate and chloride were less consumed.

Consolidated bioprocessing of wastewater cocktail in an algal biorefinery for enhanced biomass, lipid and lutein production coupled with efficient CO2 capture: An advanced optimization approach

We present a holistic approach in establishing a successful green integrated bio-refinery system with improved biomass, lipid and lutein productivity, while remediating wastewater and sequestering CO₂ with potential biodiesel and healthcare applications. To achieve this we evaluated the effect of four process parameters: CO₂% supply; acetate concentration; poultry litter waste (PLW) concentration; and light intensity on cultivation of Chlorella minutissma following the Taguchi's design of experimental technique. A four factors, three levels orthogonal array was adopted to cultivate Chlorella minutissma in specially developed waste water medium. Effect of the process parameters on biomass productivity, CO₂ fixation rate, lipid content, lutein productivity and bioremediation capacity were determined. Results obtained from individual parametric combinations and Signal/Noise (S/N) ratio responses indicated S3 (5% CO₂, 100 mg L^-1 of acetate, 10 g L^-1 of poultry litter, and 15, 000 lux of light intensity) combination as the optimum cultivation condition. Following the S3 combination a significant enhancement in biomass productivity (292 mg L^-1 d^-1) with exceedingly high CO₂ fixation rate and photosynthetic efficiency (51.51 g L^-1 d^-1 of CO₂; P.E: 15.81%) was achieved. A maximum of 169.29 mg L^-1 d^-1 of lipid with a balanced distribution of saturated and unsaturated fatty acids conformed to the international standard for biodiesel was achieved. Additionally, 7.21 mg L^-1 d^-1 of lutein productivity was also accomplished within 7 day of cultivation, while remediating up to 93-90% of nitrogenous and phosphate substrates. Statistically, the results reinforced our findings with the S/N responses and experimental observations for a particular property.

Bio-fixation of flue gas from thermal power plants with algal biomass: Overview and research perspectives

Rate of energy production is reflecting growth of nations and most of energy produced from the coal and natural gas-based thermal power plants (TPPs). Flue gas (point sources of emission) are main exhaustible form of gases that come from thermal power plants and are continuously promoting climate change and various environmental problems in global scenario. The present available technologies of flue gas treatment are energy and cost-intensive process. Among the available techniques for fixation of flue-gases at sustainable part, microalgal bio-fixation of flue gas is an alternative promising and competent technology with assurance of eco-friendly path of low energy and low-cost solution for pollution abetment with production of value added products. According to mechanism involves during photosynthetic process of microalgae, it utilizes atmospheric CO₂ and CO₂ from flue gases for their growth. Past, present and future treatment technologies for flue gas with their challenges are discussed. Recent experimental studies and commercially available bioreactors are very particular for bio-fixation of flue gas from thermal power plants are also reviewed with their future perspectives. The commercial viability of process with specific microalgal strains and utilized biomass for further value-added products are suggested with future limitations.

Bench-Scale Cultivation of Microalgae Scenedesmus almeriensis for CO2 Capture and Lutein Production

In this study, Scenedesmus almeriensis as green microalga was cultivated on bench-scale for carbon dioxide (CO2) capture and lutein production. The autotrophic cultivation of S. almeriensis was carried out by using a vertical bubble column photo-bioreactor (VBC-PBR) with a continuous flow of a gaseous mixture of oxygen (O2), nitrogen (N2), and CO2, the latter in content of 0.0–3.0 %v/v. The liquid phase was batch. S. almeriensis growth was optimized. In addition, lutein extraction was carried out by using accelerated solvent extraction with ethanol as Generally Recognized as Safe (GRAS) solvent at 67 °C and 10 MPa. Upon optimization of CO2 concentration, the maximum biomass productivity, equal to 129.24 mg·L−1·d−1, was achieved during the cultivation by using a content of CO2 equal to 3.0 %v/v and it allowed to obtain a lutein content of 8.54 mg·g−1, which was 5.6-fold higher in comparison to the analogous process carried out without CO2 addition. The ion chemical analysis in the growth medium showed that by gradually increasing CO2 content, the nutrient consumption during the growth phase also increased. This study may be of potential interest for lutein extraction at industrial scale, since it is focused on pigment production from a natural source with a concomitantly CO2 capture.

Performance evaluation of an outdoor algal biorefinery for sustainable production of biomass, lipid and lutein valorizing flue-gas carbon dioxide and wastewater cocktail

We evaluated wastewater remediation and CO₂ utilization potential of Chlorella minutissima from flue gas in a raceway pond, while synthesizing lutein and lipid for potential healthcare and biofuel application. A mix of 20% kitchen waste, 10 g L^-1 of poultry litter waste and 5% flue gas was maintained while cultivating the microalga. Complete removal of nitrate, nitrite and ammonium, 85% carbon and 91% phosphorus was observed. An average areal biomass productivity of 4.06 ± 0.12 g m^-2 day^-1 with a specific growth rate of 0.34 ± 0.03 day^-1 was observed within 9 days. Biomass productivity of 6.21 ± 0.16 g m^-2 day^-1 with a specific growth rate of 0.34 ± 0.03 day^-1 was achieved during winter. Furthermore, lipid content with appropriate fatty acid composition 1.04:1 (saturation:unsaturation) increased from 25% to 58%. Additionally, lutein productivity of 1.2 ± 0.08 mgL^-1 day^-1, while utilizing 80.74 ± 0.07 mg L^-1 day^-1 of CO₂ from 5% flue gas was obtained.

Enhancing lutein productivity of Chlamydomonas sp. via high-intensity light exposure with corresponding carotenogenic genes expression profiles

The marine microalga Chlamydomonas sp. JSC4 is a potential lutein source with high light tolerance. In this study, light intensity was manipulated to enhance cell growth and lutein production of this microalga. High lutein productivity (5.08 mg/L/d) was achieved under high light irradiation of 625 μmol/m²/s. Further increase in light intensity to 750 μmol/m²/s enhanced the biomass productivity to 1821.5 mg/L/d, but led to a decrease in lutein content. Under high light conditions, most carotenoids and chlorophyll contents decreased, while zeaxanthin and antheraxanthin contents increased. Inspection of gene expression profile shows that the lut1 and zep genes, responsible for lutein synthesis and flow of zeaxanthin into violaxanthin, respectively, were downregulated, while zeaxanthin biosynthesis gene crtZ was upregulated when the microalga was exposed to a high light intensity. This is consistent with the decrease in lutein content and increase in zeaxanthin content under high light exposure.

CO2 bio-fixation and biofuel production in an airlift photobioreactor by an isolated strain of microalgae Coelastrum sp. SM under high CO2 concentrations

Microalgae cultivation is a promising approach to remove ambient CO₂ via photosynthesis process. This paper investigates the impact of high CO₂ concentrations (6, 12, and 16%) on algae growth, CO₂ biofixation, lipid and carbohydrate contents, and nutrient removal of newly isolated microalgae, Coelastrum sp. SM. In addition, the ability of microalgae to produce biodiesel at optimal condition was studied. The microalgae were cultivated in wastewater using an airlift photobioreactor. Under 12% CO₂, the maximum biomass productivity and CO₂ fixation rate were 0.267 g L^-1 day^-1 and 0.302 g L^-1 h^-1, respectively. Total Kjeldahl nitrogen (TKN), total phosphorous (TP), nitrate, and sCOD removal efficiency were 84.01, 100, 86.811, and 73.084%, respectively. Under 12% CO₂ and at the same condition for cell growth, the highest lipid and carbohydrate contents were 3 7.91 and 58.45%, respectively. The composition of fatty acids methyl ester (FAME) of the microalga lipid was defined. Based on the obtained results and FAME profile, Coelastrum sp. SM was a suitable feedstock for biodiesel production and also, the organism had a great potential for CO₂ biofixation, which is also more suitable than any other reported strains in other related studies.

Quorum sensing inhibitory activity of the metabolome from endophytic Kwoniella sp. PY016: characterization and hybrid model-based optimization

Quorum sensing, the microbial communication system, is gaining importance as a therapeutic target against pathogens. The two key reasons for the rising demand of quorum sensing (QS) inhibitory molecules are low selective pressure to develop resistance by pathogens and possibility of more species-specific effects. Due to complex interactions in a unique niche of live plant tissues, endophytes, as a survival mechanism, potentially produce various bioactive compounds such as QS inhibitors. We report the isolation of an endophytic fungus Kwoniella sp. PY016 from the medicinal plant "Bahera" (Terminalia bellirica), which exhibits substantial quorum sensing inhibition and anti-biofilm activities against the standard test organism, Chromobacterium violaceum. Sugar, sugar alcohol, carboxylic acid, lipid, and phenolic classes of metabolites (predominantly xylitol) are responsible components of the metabolome for the desired bioactivity. A judicious combination of single-factor-at-a-time strategy and artificial neural network modeling combined with genetic algorithm was employed for the selection and optimization of the critical process and medium parameters. Through this newly adopted hybrid model-based optimization, the quorum sensing inhibitory activity of the endophytic metabolome was increased by ~ 30%. This is the first report on optimization of QS inhibitory activity from any fungal endophyte using such a hybrid advanced approach.

Enhancing cell growth and lutein productivity of Desmodesmus sp. F51 by optimal utilization of inorganic carbon sources and ammonium salt

The type and concentration of inorganic carbon and nitrogen sources were manipulated to improve cell growth and lutein productivity of Desmodesmus sp. F51. Using nitrate as nitrogen source, the better cell growth and lutein accumulation were obtained under 2.5% CO₂ supply when compared to the addition of NaHCO₃ or Na₂CO₃. To solve the pH variation problem of ammonium consumption, the strategy of using dual carbon sources (NaHCO₃ and CO₂) was explored. A lower bicarbonate-C: ammonium-N ratio led to a lower culture pH as well as lower lutein productivity, but significantly enhanced the auto-flocculation efficiency of the microalgal cells. The highest biomass productivity (939mg/L/d) and lutein productivity (5.22mg/L/d) were obtained when the bicarbonate-C/ammonium-N ratio and ammonium-N concentration were 1:1 and 150mg/L, respectively. The lutein productivity of 5.22mg/L/d is the highest value ever reported in the literature using batch phototrophic cultivation.

Simultaneous microalgal biomass production and CO2 fixation by cultivating Chlorella sp. GD with aquaculture wastewater and boiler flue gas

A microalgal strain, Chlorella sp. GD, cultivated in aquaculture wastewater (AW) aerated with boiler flue gas, was investigated. When AW from a grouper fish farm was supplemented with additional nutrients, the microalgal biomass productivity after 7days of culture was 0.794gL^-1d^-1. CO₂ fixation efficiencies of the microalgal strains aerated with 0.05, 0.1, 0.2, and 0.3vvm of boiler flue gas (containing approximately 8% CO₂) were 53, 51, 38, and 30%, respectively. When the microalgal strain was cultured with boiler flue gas in nutrient-added AW, biomass productivity increased to 0.892gL^-1d^-1. In semi-continuous cultures, average biomass productivities of the microalgal strain in 2-day, 3-day, and 4-day replacement cultures were 1.296, 0.985, and 0.944gL^-1d^-1, respectively. These results demonstrate the potential of using Chlorella sp. GD cultivations in AW aerated with boiler flue gas for reusing water resources, reducing CO₂ emission, and producing microalgal biomass.

Integrated in situ transesterification for improved biodiesel production from oleaginous yeast: a value proposition for possible industrial implication

An integrated in situ transesterification process was developed in this study for energy and cost-efficient biodiesel production from oleaginous yeast biomass.

Modelling of oxygen-evolving-complex ionization dynamics for energy-efficient production of microalgal biomass, pigment and lipid with carbon capture: an engineering vision for a biorefinery

Development of an algal growth kinetics model, incorporating oxygen-evolving-complex ionization dynamics, for sustainable production of algal biomass, lipid, and chlorophyll (with associated carbon dioxide capture) in an algal biorefinery.

Rationally leveraging mixotrophic growth of microalgae in different photobioreactor configurations for reducing the carbon footprint of an algal biorefinery: a techno-economic perspective

Experimental set-up to study mixotrophy in Chlorella vulgaris.

An integrated salinity-driven workflow for rapid lipid enhancement in green microalgae for biodiesel application

A laboratory based integrated approach was undertaken for improvement of lipid accumulation in green microalgae under sodium chloride (NaCl) stress.

Photosynthesis of cyanobacteria in a miniaturized optofluidic waveguide platform

We investigated the effect of increasing the optical penetration length, inside polydimethylsiloxane (PDMS)-based photobioreactors (PBRs), upon the photosynthetic cell growth of cyanobacteria.