College of Resources and Environmental Sciences, Beijing Key Laboratory of Biodiversity and Organic Farming, China Agricultural University, Beijing 100193, China; Organic Recycling Institute (Suzhou) of China Agricultural University, Wuzhong District, Suzhou 215128, China.
College of Resources and Environmental Sciences, Beijing Key Laboratory of Biodiversity and Organic Farming, China Agricultural University, Beijing 100193, China.
Sci Total Environ. 2024 Nov 15;951:175565. doi: 10.1016/j.scitotenv.2024.175565. Epub 2024 Aug 14.
Long-chain fatty acids (LCFAs) are recognized as a significant inhibitory factor in anaerobic digestion of food waste (FW), yet they are inevitably present in FW due to lipid hydrolysis. Given their distinct synthesis mechanism from traditional anaerobic digestion, little is known about the effect of LCFAs on FW acidogenic fermentation. This study reveals that total volatile fatty acids (VFAs) production increased by 9.98 % and 4.03 % under stearic acid and oleic acid loading, respectively. Acetic acid production increased by 20.66 % under stearic acid loading compared to the control group (CK). However, the LCFA stress restricted the degradation of solid organic matter, particularly under oleic acid stress. Analysis of microbial community structure and quorum sensing (QS) indicates that LCFA stress enhanced the relative abundance of Lactobacillus and Klebsiella. In QS system, the relative abundance of luxS declined from 0.157 % to 0.116 % and 0.125 % under oleic acid and stearic acid stress, respectively. LCFA stress limited the Autoinducer-2 (AI-2) biosynthesis, suggesting that microorganisms cannot use QS to resist the LCFA stress. Metagenomic sequencing showed that LCFA stress promoted acetic acid production via the conversion of pyruvate and acetyl-CoA to acetate. Direct conversion of pyruvate to acetic acid increased by 47.23 % compared to the CK group, accounting for the enhanced acetic acid production under stearic acid loading. The abundance of β-oxidation pathway under stearic acid loading was lower than under oleic acid loading. Overall, the stimulating direct conversion of pyruvate plays a pivotal role in enhancing acetic acid biosynthesis under stearic acid loading, providing insights into the effect of LCFA on mechanism of FW acidogenic fermentation.
长链脂肪酸（LCFAs）被认为是抑制食物垃圾（FW）厌氧消化的重要因素，但由于脂肪水解，它们不可避免地存在于 FW 中。鉴于它们与传统厌氧消化的独特合成机制不同，对于 LCFAs 对 FW 产酸发酵的影响知之甚少。本研究表明，在硬脂酸和油酸负荷下，总挥发性脂肪酸（VFAs）的产量分别增加了 9.98%和 4.03%。与对照组（CK）相比，硬脂酸负荷下乙酸产量增加了 20.66%。然而，LCFA 应激限制了固体有机物的降解，特别是在油酸应激下。微生物群落结构和群体感应（QS）分析表明，LCFA 应激增强了乳杆菌和克雷伯氏菌的相对丰度。在 QS 系统中，油酸和硬脂酸胁迫下 luxS 的相对丰度分别从 0.157%下降到 0.116%和 0.125%。LCFA 应激限制了 Autoinducer-2（AI-2）的生物合成，表明微生物不能利用 QS 来抵抗 LCFA 应激。宏基因组测序表明，LCFA 应激通过丙酮酸和乙酰辅酶 A 转化为乙酸来促进乙酸的产生。与 CK 组相比，丙酮酸直接转化为乙酸增加了 47.23%，这解释了硬脂酸负荷下乙酸产量的增加。硬脂酸负荷下β-氧化途径的丰度低于油酸负荷下。总的来说，刺激丙酮酸的直接转化在硬脂酸负荷下增强乙酸生物合成中起着关键作用，为理解 LCFA 对 FW 产酸发酵机制的影响提供了新视角。
