The role of lipids in fermentative propionate production from the co-fermentation of lipid and food waste

Food waste(FW)is a promising renewable low-cost biomass substrate for enhancing the economic feasibility of fermentative propionate production.Although lipids,a common component of food waste,can be used as a carbon source to enhance the production of volatile fatty acids(VFAs)during co-fermentation,few studies have evaluated the potential for directional propionate production from the co-fermentation of lipids and FW.In this study,co-fermentation experiments were conducted using different combinations of lipids and FW for VFA production.The contributions of lipids and FW to propionate production,hydrolysis of substrates,and microbial composition during.cofermentation were evaluated.The results revealed that lipids shifted the fermentation type of FW from butyric to propionic acid fermentation.Based on the estimated propionate production kinetic parameters,the maximum propionate productivity increased significantly with an increase in lipid content,reaching 6.23 g propionate/(L·d)at a lipid content of 50%.Propionate-producing bacteria Prevotella,Veillonella,and norank f Propionibacteriaceae were enriched in the presence of lipids,and the succinate pathway was identified as a prominent fermentation route for propionate production.Moreover,the Kyoto Encyclopedia of Genes and Genomes functional annotation revealed that the expression of functional genes associated with amino acid metabolism was enhanced by the presence of lipids.Collectively,these findings will contribute to gaining a better understanding of targeted propionate production from FW.