Recovery of volatile ethanol gas via microalgal-bacterial consortium: Ethanol-to-acetate conversion pathway boosts...

The pharmaceutical industry, an essential sector of the global economy, heavily relies on ethanol solvents, which leads to significant volatile organic compounds (VOCs) emissions. As a sustainable treatment method aligning with carbon reduction goals, this study proposed and demonstrated a synergistic approach of using microalgae (Chlorella sorokiniana FACHB-24) and acetic acid bacteria (Acetobacter pasteurianus CICC 20056) to recover ethanol into value-added products (algal lipids). In the innovative co-culture, A. pasteurianus oxidizes ethanol to acetic acid, which is fed to algae for lipid production. This method increased biomass and lipid yield by 21.29% and 150.16% (p < 0.05), respectively, compared to microalgae directly using ethanol. Some operational parameters including ethanol concentration, bacterial-algal biomass ratio, pH value, and light intensity made influence on lipid production. Under the optimal conditions (1.0% v/v ethanol concentration, 1:10 bacterial-algal biomass ratio, pH 6.5, and 5000 lux light intensity), the maximal biomass and lipid yields were 572.5 mg L^-1 and 161.1 mg L^-1 (26.7% lipid content), respectively. In the harvested lipid from microalgae, C16 - C18 fatty acids made up 98.22% of the total fatty acid methyl esters content. In proteomic comparison of the single culture and co-culture, the conversion of ethanol to acetate by A. pasteurianus provides C. sorokiniana with a more efficient acetyl-CoA source by bypassing energy-intensive glycolysis and directly enhancing lipid synthesis. This study provides a solution to increasing the lipid production from ethanol gas as a sustainable VOCs management of pharmaceutical industry.