Enhanced anaerobic fermentation of potato waste for volatile fatty acid production by dilute sulfuric acid pretreatment: Performance, microbial community, and gene expression

Anaerobic fermentation of potato waste for volatile fatty acid (VFA) production is a promising pathway for resource utilization. Hydrolysis of potato waste is the bottleneck for efficient VFA production. Dilute sulfuric acid pretreatment is an effective pretreatment technology for improving hydrolysis. In this study, the effects of 1 %, 2 %, 4 %, and 8 % sulfuric acid pretreatment on VFA production, microbial community, and functional gene expression in anaerobic fermentation of potato waste were investigated. Results showed that the 1 % sulfuric acid pretreatment had the highest soluble carbohydrate concentration, reaching 811.0 mg/g dry weight, which was 45.2 times higher than the unpretreated. The corresponding VFA yield reached a maximum of 373.4 mg/g volatile solids, which was 17.8 %, 15.1 %, 9.4 %, and 19.9 % higher than that of other concentration sulfuric acid pretreatments. Meanwhile, VFA production shifted from butyrate-type to acetate-type fermentation with the increase of sulfuric acid concentration. High concentration sulfuric acid pretreatment decreased the microbial diversity. Further, pretreatment of sulfuric acid concentration significantly affected the microbial community, leading to the shift in VFA composition. Expression of functional gene also explained the conversion of butyrate to acetate-type. A profit of 42.9 €/t was estimated for the 1 % sulfuric acid pretreated potato waste to produce VFAs. Thus, the 1 % sulfuric acid was the optimal pretreatment concentration of potato waste for VFA production. This study provides a theoretical reference for VFA production from potato waste.