Substrate toxicity would limit the upgrading of waste biomass to medium-chain fatty acids (MCFAs). In this work, two fermentation modes of electro-fermentation (EF) and traditional fermentation (TF) with different concentration of liquor fermentation waste (20%, 40%, 60%) were used for MCFAs production as well as mechanism investigation. The highest caproate (4.04 g/L) and butyrate (13.96 g/L) concentrations were obtained by EF at 40% substrate concentration. TF experiments showed that the substrate concentration above 40% severely inhibited ethanol oxidation and products formation. Compared with TF mode, the total substrates consumption and product yields under EF mode were significantly increased by 2.6%∼43.5% and 54.0%∼83.0%, respectively. Microbial analysis indicated that EF effectively alleviated substrate toxicity and enriched chain elongation bacteria, particularly Clostridium_sensu_stricto 12, thereby promoting ethanol oxidation and products formation. Caproiciproducens tolerated high-concentration substrates to ensure normal lactate metabolism. This study provides a new way to produce MCFAs from high concentration wastewater.

底物毒性会限制废弃生物质向中链脂肪酸 (MCFA) 的升级。在这项工作中，使用不同浓度（20%、40%、60%）的电发酵（EF）和传统发酵（TF）两种发酵模式进行 MCFAs 生产和机理研究。EF 在 40% 底物浓度下获得了最高的己酸盐 (4.04 g/L) 和丁酸盐 (13.96 g/L) 浓度。TF 实验表明，底物浓度超过 40% 会严重抑制乙醇氧化和产物形成。与TF模式相比，EF模式下的总底物消耗和产物收率分别显着提高了2.6%～43.5%和54.0%～83.0%。Clostridium_sensu_stricto 12，从而促进乙醇氧化和产物形成。Caproiciproducens耐受高浓度底物以确保正常的乳酸代谢。该研究提供了一种利用高浓度废水生产MCFAs的新途径。