Metatranscriptomic insights of the metabolic process enhancement during food wastes fermentation driven by linear alkylbenzene sulphonates

Abstract

In this study, the approach of stimulating the production of volatile fatty acids (VFAs) during food wastes (FW) fermentation by linear alkylbenzene sulphonates (LAS) is proposed and the underlying mechanisms from a metagenomic perspective are analyzed. The results show that with an appropriate level of LAS (50 mg/L), VFA production is greatly enhanced (11854 versus 1825 mg COD/L) with the increased proportions of high-value long-chain ones. Mechanistic explorations indicate that LAS contributes to the solubilization/hydrolysis of the main organic components in FW (i.e., carbohydrates, proteins and lipids) due to the amphipathic features. Besides, LAS would interact with the cell membranes and increase the cell permeability to promote the membrane transport of substrates into the functional microorganisms for further metabolisms. The metagenomic analysis demonstrates that the critical genes involved in hydrolase secretion (i.e., bglX, pepD and lip), ABC transporter (i.e., rfbA and lolD), main substrate metabolism (especially the proteins and lipids, i.e., glsA and glpK) and fatty acid biosynthesis (i.e., accA, accC and accD) all highly expressed in LAS-conditioned reactors. The upregulation of these encoding genes stimulates microbial metabolic activities and improves the production rates of VFAs. Besides, the distribution of functional microbial populations and their associations with genetic expressions in different reactors were investigated. This study provides profound information on the stimulating effects of LAS on FW fermentation for VFA production from genetic and functional perspectives.