Microbial protein and lipid production from biogas and syngas using extremophilic methanotroph Methylacidiphilum fumariolicum Pic

Verrucomicrobial methane-oxidizing bacteria have a broad metabolic versatility, allowing them to utilize a wide range of gaseous feedstocks, highlighting their potential as robust biocatalysts for the valorization of process gases in gas-based biorefineries. In this study, the extremophilic bacteria Methylacidiphilum fumariolicum Pic was cultivated using synthetic biogas, H 2 supplemented biogas, and syngas for the production of microbial protein and lipids. Growth based on simultaneous utilization of CH 4 and H 2 enhanced microbial biomass production, reaching biomass production yield of 1.49 ± 0.11 g dry weight /g carbon consumed , twice that obtained with biogas. Growth was also sustained on syngas with CO removal rates of 5.0 ± 0.9 mg CO·L −1 h −1 , although CO inhibition reduced biomass productivity. Proteins represented the major biomass fraction, ranging from 0.43 to 0.63 g protein /g dry weight . The high protein content and well-balanced amino acid composition indicate potential suitability for aquafeed applications. Lipids accounted for 0.13 to 0.34 g lipid /g dry weight and were predominantly composed of branched-chain fatty acids (58–68 % of total fatty acids). Overall, these findings expand the opportunities for utilizing extremophilic methane-oxidizing bacteria in gas-based biorefineries aimed at microbial protein production and its potential valorization as an aquafeed ingredient.