Upscaled valorization of food waste into single-cell proteins through Yarrowia lipolytica

Liquid effluents generated during the anaerobic fermentation (AF) of organic wastes contain high short-chain fatty acids (SCFAs) concentrations that serve as efficient carbon sources for microbial oil production. However, the high nitrogen content typically found in these effluents may limit lipid accumulation in yeasts, while favoring single cell protein (SCP) production. In this sense, the present study focused on the upscaled production of SCP in 50-L bioreactor using AF effluents derived from carbohydrate-rich food waste (carbohydrate effluent, CE) and lipid-rich food waste (lipid effluent, LE). These media contained up to 23 g/L of SCFAs, which served as the main carbon source for Yarrowia lipolytica ACA DC50109. With both real effluents, SCP production (66.6 % w/w and 55.5 % w/w) and biomass concentration (7.5 g CDW/L and 11.1 g CDW/L) were higher than for synthetic media. Specifically, the achieved SCP content and biomass concentrations were 59.5 % w/w and 4.8 g/L with synthetic CE, as well as 53.1 % w/w and 4.4 g/L for synthetic LE. Aspartic acid, glutamic acid, lysine and alanine, which enhance structural integrity, mechanical strength and material durability of SCP-based biopolymers, were the prevalent amino acids in all cases. Overall, this is the first work to validate the conversion of real SCFAs-rich effluents into SCP at pilot scale, establishing a novel strategy for waste revalorization and a promising microbial platform for future biopolymer production.