Enhanced volatile fatty acid production from co-fermentation of spent mushroom waste and food waste with rumen microbes: Performance and mechanism.

OBJECTIVE: Co-fermentation of lignocellulosic biomass and food waste (FW) can enhance the production of volatile fatty acids (VFAs) during anaerobic fermentation. However, the effect and mechanism of co-fermentation of Auricularia auricula waste (AW) with FW remains unclear. This study aimed to investigate the effect and mechanism of co-fermentation of Auricularia auricula waste (AW) with food waste (FW) on volatile fatty acid (VFA) production. METHODS: Anaerobic fermentation experiments were conducted at different AW/FW ratios (1:0, 1:1, 2:1, 3:1, 4:1, 0:1) based on volatile solids (VS). VS removal and VFA concentration were measured, and metagenomic sequencing was performed to elucidate the underlying enhancement mechanism. RESULTS: Co-fermentation significantly improved VS removal and VFA production, with both parameters increasing as the proportion of FW increased. The highest VS removal (48.9%) and VFA concentration (7929 mg/L) were achieved at an AW/FW ratio of 1:1, which were approximately double those of AW alone (22.4% and 3659 mg/L, respectively). Metagenomic analysis revealed that co-fermentation enriched bacterial genera such as Rummeliibacillus (25.4%) and Leuconostoc (9.2%), while Fungal genera Piromyces and Neocallimastix became dominant. Moreover, co-fermentation increased the relative abundance of carbohydrate-active enzymes and activated key functional genes in the VFA production pathway (e.g., ackA, PTA, MDH, HBD). CONCLUSION: Co-fermentation of AW and FW significantly enhanced the hydrolysis and VFA production. The enhancement mechanism of VFA production during co-fermentation primarily involved the synergistic interaction between substrate nutrient complementation and efficient microbial community. This study provides a feasible strategy for efficient VFA production from spent mushroom waste.