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Microalgae synthesize valuable compounds like pigments, proteins, lipids and carbohydrates under stress conditions, which make them an interesting feedstock for different industries. The effect of GABA (Gamma-aminobutyric acid) supplementation under salinity stress conditions was investigated on growth, biomass, pigments, lipid and protein content of Pseudochlorella pringsheimii. Between the varying treatments, 5 g/L NaCl combined with 2.5 mM GABA was observed as the best concentration for stimulating the production of bioactive compounds in microalga P. pringsheimii. The results revealed a significant increase in biomass content by 93.24 %, compared with the control. Moreover, a significant increase was also observed in the production of chlorophyll (chl) a, chlorophyll (chl) b, total carotenoids (car), protein and lipid content by 112.15 %, 84 %, 29.94 %, 23.08 % and 35.63 %, respectively. However, as compared to control and salinity stress alone, the total carbohydrate content was sharply declined by 52.30 % and 101.79 % in GABA supplemented groups. In addition, the presence of fatty acids and different biomolecules were also confirmed by GC–MS and FTIR analysis. The existence of different essential and non-essential amino acids in substantial amounts was validated by UHPLC analysis. Collectively, the present work contributes to a novel strategy for boosting the coproduction of biomass, lipids, proteins and pigments in P. pringsheimii under unfavorable conditions.

Abstract Ageratum conyzoides, an herb found throughout the year, is generally considered as a weed: it causes reduction in soil productivity and leads to health hazards for cattle and humans. However, its biomass can easily represent a cost‐effective source, which can be used for lignocellulosic biofuel production. The conversion of lignocellulosic biomass to ethanol has drawn much attention in recent times due to abundance of biomass. In the present study, the cellulose and hemicellulose biomass of the leaf and stem of A. conyzoides was converted to sugars using acid hydrolysis.146.01 ± 02 mg/g of fermentable sugar was obtained from A. conyzoides. The maximum ethanol concentration 11.89 g/L was obtained after 7 days. Scanning electron microscopy was used to characterize the surface morphology after acid hydrolysis of biomass. In the current study, the residues of acid hydrolysis and fermented wastewater was used for biogas production through anaerobic digestion. The yield of biogas from the residues of acid hydrolysis and fermented wastewater was 204 L kg−1VS. The results obtained indicate that A. conyzoides may be considered as a promising feedstock for bioethanol and biogas production.

Oleaginous microalgae are being used extensively worldwide for the development of integrated sustainable environment technologies. Microalgae can be used to remove environmental pollutants and simultaneous extraction of biofuels from the same culture. Microalgae have also evolved different intracellular and extracellular mechanisms to resist the toxic effects of different environmental pollutants that stimulate lipid accumulation. The advancements in microalgae omics with the use of recent tools like H1NMR spectroscopy, GC-MS, FTIR spectroscopy, ICP-MS, LC-MS can provide deep insights towards understanding the various underlying mechanisms to resist environmental stresses. They are a promising candidate towards Green Bioremediation and Biofuel production.

Cell disruption and lipid extraction methods for macroalgae are not well reported. Therefore, we compared various lipid extraction methods and extraction efficiency of various solvents to improve lipid yields from Oedogonium fresh water macroalgae. Lipid extraction was done by 2 methods viz., modified Bligh and Dyer method and soxhlet extraction using either single solvents or mixtures. In soxhlet extraction method five solvents were used (1) Hexane commonly used solvent for lipid extractions, (2) chloroform: methanol (2:1), (3) Chloroform: hexane (1:1), (4) Chloroform: hexane (1:2), (5) Dichloromethane + methanol (2:1). To improve lipid extraction yields, various cell disruption methods were also compared during the present study. Impurities of chlorophyll and protein were also detected in the extracted lipids. Hydrothermal liquefaction of algal biomass with TiO2 was also conducted at 300 °C. HTL was more effective by which 23.3 wt% of bio-crude oil was obtained. Keywords: Oedogonium, Macroalgae, Cell disruption, Lipid, Biodiesel, HTL