氨氮对餐厨垃圾厌氧消化性能及微生物群落的影响

为探析氨氮（TAN）对餐厨垃圾厌氧消化性能及微生物群落的影响，在串联批次实验中引入氨氮胁迫，结合Miseq高通量测序分析，研究了不同TAN浓度下厌氧消化系统的过程参数响应以及微生物群落动态.结果显示，随TAN增加，甲烷回收率从（96.53±2.66）%下降至（63.13±0.73）%，消化时间从435h延长至915h，连续驯化下，TAN为3000mg/L的实验组产气性能完全恢复，而高氨氮实验组（TAN³6000mg/L）仍处于抑制状态.相较于乙酸代谢而言，长链挥发性脂肪酸（LCVFAs）代谢对TAN的耐受度更高（6000mg/L），但一旦被抑制，其功能难以通过驯化恢复.从微生物层面上看，高丰度且功能冗余的水解酸化细菌保证了各TAN梯度下的水解酸化作用；氨氮敏感的Methanosaeta和Methanospirillum也能通过驯化被耐氨的Methanosarcina和Methanoculleus取代，从而维持系统产甲烷功能；相比之下，产氢产乙酸菌功能高度专一，仅C₄~C₁₈降解菌Syntrophomonas和丙酸降解菌Pelotomaculum被检测到，在连续的高氨氮暴露下，前者的丰度虽有一定程度的恢复，但后者未能被驯化，最终系统出现以丙酸为主的LCVFAs积累，产气性能恶化.可见， LCVFAs的互营降解才是氨抑制失稳的关键环节.

Effects of ammonia on anaerobic digestion of food waste: Process performance and microbial community

A series of batch experiments were conducted under ammonia-N stress conditions to investigate the effects of ammonium (TAN) on performance and microbial community during the anaerobic digestion (AD) process of food waste. At different TAN levels, the response of AD process parameters and the dynamics of microbial communities were investigated by physico-chemical analysis along with Miseq high-throughput sequencing analysis. Results showed that, with the increase of TAN, the methane recovery rate decreased from (96.53±2.66)% to (63.13±0.73)% while the digestion time increased from 435h to 915h. After continuous acclimation, the gas production performance was completely recovered in the test group with TAN concentration of 3000mg/L. However, the gas production in the group with high ammonia concentration (³6000mg/L) was still inhibited and did not recovered by acclimation. Compared with acetate metabolism, the metabolism of long-chain volatile fatty acids (LCVFAs) was more tolerant to ammonia level (6000mg/L), but difficult to recover by acclimation if inhibited. At the microbial communities, the high abundance of hydrolytic and fermentative bacteria with redundant function ensured adequate hydrolysis and acidification at different TAN concentrations. Ammonia-sensitive Methanosaeta and Methanospirillum could also be replaced by ammonia-resistant Methanosarcina and Methanoculleus via acclimation, and thus ensure methanogenesis. In comparison, acetogenic bacteria featured with highly specialized function, and only the C₄~C₁₈ and propionate degraded Syntrophomonas and Pelotomaculum were detected. Under continuous high ammonia exposure, the abundance of the former bacteria recovered to a certain degree, while the latter could not be acclimatized. Eventually, the AD system was observed to accumulate LCVFAs (mainly propionate), and the gas production process was deteriorated. Therefore, the key contributor to ammonia inhibition turned out to be the syntrophic degradation of LCVFAs.