Study On The Mechanism Of Ammonia Inhibition Instability In Anaerobic Digestion System Of Food Waste Based On Multi-omics

In order to reveal the mechanism of ammonia inhibition instability during anaerobic digestion,and to clarify the key microorganisms responsible for instability,so as to provide a data basis for the development of more efficient and targeted microbial regulation technologies,a laboratory-scale semi-continuous anaerobic digestion experiment under ammonia stress was carried out,and high-protein food waste was used as a substrate to induce endogenous ammonia accumulation.Techniques including physical-chemical analysis and multi-omics analysis combining metagenomics and metaproteomics were performed to clarify the response characteristics of reactor performance and its microbial response mechanism during the accumulation of endogenous ammonia.The results showed that:1 When TAN>2300mg/L,ammonia could inhibit the degradation of amino acids by inhibiting the metabolic activity of the dominant amino acid degrading bacterium Aminivibrio,resulting in SCOD accumulation in the form of amino acids.However,under long-term ammonia stress,ammonia-tolerant Tisierella,Lutispora and Aminobacterium could restore amino acid degradation activity.2 Ammonia with TAN>2300mg/L could also inhibit acetate metabolism by inhibiting the expression activity of methyl coenzyme M reductase of the dominant acetotrophic methanogen Methanothrix,resulting in a large accumulation of acetate and the accumulation of other VFA such as propionate butyrate and valerate through feedback effect.As a result,the gas production performance was further deteriorated and the reactor was facing instability.But under long-term ammonia stress,the enhancement of the acetotrophic methanogenesis function of the ammonia-tolerant Methanosarcina could restore acetate metabolism,the feedback effect was relieved,and other VFA metabolism and gas production performance were restored.Subsequently,due to the shift of the dominant acetate metabolic pathway to the more tolerant syntrophic acetate oxidation-hydrogenotrophic methanogenesis dominated by Clostridium ultunense and Methanosarcina,the stability of the acetate metabolic process was even further strengthened.3 When TAN>4500mg/L,ammonia would inhibit the metabolic activity of the MMC pathway of the dominant syntrophic propionate-oxidizing bacteria Pelotomaculum by inhibiting the gene abundance and expression activity of the succinyl-Co A synthase encoding gene suc C / D,leading to the complete inhibition of the system’s syntrophic propionate oxidation process without recovery.As a result,a large amount of propionate was accumulated,the gas production performance decreased,and the reactor eventually collapsed.This study revealed the response characters of anaerobic digesters performance during the accumulation of endogenous ammonia,and found that propionate metabolism is a key link of process instability,and SCOD may be a potential early warning factor for instability.The responses of microorganisms and their functions to endogenous ammonia stress were deeply analyzed,and it was revealed that the inhibition of syntrophic propionate oxidation by ammonia was the root cause of reactor instability,and syntrophic propionate-oxidizing bacteria were the key microorganisms for the instability,which proved the feasibility of microbial regulation in anaerobic digesters.