Study on the synergistic pretreatment of sludge with surface active agents and sophorolipids to enhance acid production from lignocellulose carbon sources by anaerobic fermentation

In order to solve the slow hydrolysis and low acid production efficiency during biomass anaerobic fermentation, this study adopted four surfactants (PB 40, SDS, SDBS, F127) combined with sophorolipid (SL) for synergistic pretreatment to enhance volatile fatty acids (VFAs) production from lignocellulose and sludge co-fermentation. The effects of different synergistic pretreatment methods on VFAs yield, acid component distribution, organic matter dissolution and microbial community structure were systematically investigated. Results showed that the combined pretreatment effectively improved acid production efficiency by destroying substrate structure, accelerating organic dissolution and optimizing microbial community, which was closely related to surfactant types. The SL + PB 40 group exhibited the maximum VFAs concentration of 5883.33 mg/L, 69 % higher than that of SL group (3474.23 mg/L), and the proportion of acetic acid reached 88 %. Microbial analysis revealed that SL + PB 40 enriched Firmicutes and Lactobacillus, which dominated carbohydrate hydrolysis and protein degradation respectively, forming a synergistic metabolic network to strengthen substrate utilization and boost VFAs synthesis. This study provides a solid theoretical basis and technical reference for the resource utilization of biomass and the enhancement of acid production in anaerobic fermentation.