Exploring the Effect of Lipid Loading on Acidogenic Fermentation of Food Waste: Insights from Microbiome, Quorum Sensing and Carbon Metabolic Pathway

The high lipid loading in food waste (FW) is widely regarded as one of the main bottlenecks in the traditional anaerobic digestion, but the effect of lipid on FW acidogenic fermentation has been historically ignored. This study attempted to reveal the influence of lipid loading on volatile fatty acids (VFAs) production and the corresponding synthesis mechanisms during FW acidogenic fermentation. The VFAs production reached 27.10 +/- 1.00 g COD/L when the lipid loading comprised 25 % of the FW dry weight, increasing by 36.88 % compared to the CK group. Lactobacillus, with a relative abundance of 59.43 %, was the predominant genus under lipid loading. In quorum sensing (QS) system, the relative abundance of luxS that is involved in the biosynthetic pathway of the Autoinducer-2 (AI-2) signal molecule increased from 0.066 % to 0.10 % in the presence of lipid. The relative abundance of Genetic Information Processing increased from 16.36 % to 24.25 % under lipid loading, with up-regulation of Translation and Replication and repair. Lipid loading not only promoted the conversion of acetyl-CoA to acetic acid, as evidenced by a 1.36-fold increase in pta gene abundance, but also concurrently suppressed the consumption of acetic acid, reflected in the 96.83 % and 77.16 % decreases in ALDH and aldB abundance, thus accumulating acetic acid. Carbon emission was also constrained under lipid loading, in which the conversion from formate to CO2 and passing Tricarboxylic acid (TCA) cycle were restricted over 60 %. Together, lipid loading in FW represents a potential strategy for enhancing VFAs production in FW acidogenic fermentation.