Microbial biomass production from enzymatically saccharified organic municipal waste and present microbial inhibitors

The study investigated the potential of the organic fraction of municipal solid waste (OFMSW) for microbial biomass production. The compositional analysis of OFMSW showed richness in sugars, proteins, lipids, organic acids, and ethanol, suggesting promising cheap cultivation feedstock if inhibitory compounds are sustainably detoxified. The enzymatic hydrolysis with Cellic® CTec3 and AMG® 300 L BrewQ (Novozymes A/S) demonstrated excellent saccharification of sugar polymer, reaching 92% glucan hydrolysis and 70% xylan hydrolysis. However, higher enzymatic dosages led to a rise in the total organic acids content, potentially causing increased microbial inhibition. Full hydrolysate and hydrolysate after solids removal were cultivated with seven robust microbial strains. Cultivation on hydrolysate with solids showed consumption of sugars and organic acids solely by commercial backer yeast Saccharomyces cerevisiae. Removal of solids from hydrolysate resulted in increased performance of tested strains, showing consumption of measured organic acids and ethanol by S. cerevisiae, Yarrowia lipolytica DSM 8218, and Cutaneotrichosporon oleaginosus ATCC 20509. Remarkably, the investigation of biomass production revealed superior cell mass formation and detoxification by S. cerevisiae, resulting in 18.9 g of biomass/L hydrolysate with 50% of crude protein (w/w) in shake flasks and 13.2 g/L of hydrolase with 46% of crude protein (w/w) in a 5-L bioreactor. Furthermore, bioreactor cultivation confirmed organic acids and ethanol conversion into biomass, highlighting S. cerevisiae’s suitability for utilizing OFMSW for microbial biomass production. These findings contribute to advancements in biowaste-to-fodder conversion, promoting the development of a more sustainable circular economy. Graphical abstract: (Figure presented.)