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A green extraction method is developed using partially hydrolysed microalgal cells grown in biocompatible solvent for simultaneous cultivation and extraction of bioproducts from a highly efficient permeabilized microalgal cell with enhanced biomass and lipid content for potential use in biodiesel production. Incomplete digestion of cell wall was achieved by regulating the incubation time of the enzymatic pretreatment of the microalgal cells. 15.77% increase in lipid content was seen when untreated cells were cultured with biocompatible solvent, while cultivation of these enzymatically pretreated cells with biocompatible solvent, the lipid content increased by 53.33% and 22% higher carotenoid content was observed as compared to conventional extraction. The total fatty acids obtained after 1st and 2nd extractions in untreated samples were 67.82%, while those in enzymatically partially digested samples were 91.94%. The untreated and partially enzymatically predigested strain showed suitable properties for quality biodiesel production as per international recommendations. The cost benefit analysis of the overall process showed the use of biocompatible solvent coupled to enzymatically predigested biomass was a favorable option as compared to conventional extraction., 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 Elsevier Inc. All rights reserved.)

Recovery of waste CO2 from flue gas involves two phase gas–liquid interactions for application in enhanced microalgal growth, CO2 bio-fixation and increased production of microalgal lipids for 4th generation biofuels. Mineralized CO2 as bicarbonate between pH 10 and 7 constitutes the major inorganic carbon for phototrophic microalgae. Consolidating Carbon Capture and Usage (CCU) technology with microalgal lipid synthesis, the present work exhibits design and optimization of a microbubble assisted CO2 sequestration reactor to recover CO2 from low concentration sources (5% v/v) and maximize microalgal lipid productivity without any nutrient stress. A venturi microbubble generator was amalgamated with a bubble column and the Reynolds number was used to define the hydrodynamic flow regime. At a steady volumetric liquid flow rate QL, corresponding to laminar flow conditions, the gas flow rate QG was varied in the range 0.1–1 L min−1 to determine the volumetric mass transfer coefficient KLa and the CO2 mass transfer efficiency. KLa and QG values were found to be linearly dependent in the QG range 0.1–0.7 L min−1, while CO2 capture efficiencies in the range 86% to 98% were obtained. The optimized medium recirculation sufficed for culture agitation and further aeration for mixing was not required. A correlation coefficient was derived, relating the change in gas–liquid interfacial area with the change in QG. The resultant system achieved a biomass yield of 0.454 g L−1 and a carbon content of 38.9% volatile suspended solids (VSS). Furthermore, a lipid accumulation of 35.9% on a dry cell weight basis and a lipid productivity of 11.64 mg L−1 d−1 exhibited feasible valorisation of sequestered carbon. [ABSTRACT FROM AUTHOR]