Two-stage fermentation of food waste

This study investigates a two-stage fermentation process to convert food waste into propionate by first driving microbial metabolism toward lactate production using two different mixed inocula, which then serve as the intermediate for propionate production. With both inocula, lactate was effectively consumed and converted into propionate and acetate, with propionate concentrations reaching up to 17.90±0.35 g·L-1, representing the main metabolite (45.51±1.81 % g of total COD metabolites). This production was associated with the growth of Anaerosporobacter, Sporanaerobacter, Tyzzerella and some Clostridium genera. Overall, these results demonstrate that a two-stage fermentation strategy can efficiently target high propionate concentrations and reasonable selectivity using mixed cultures.