Improved anaerobic digestion under ammonia stress by regulating microbiome and enzyme to enhance VFAs bioconversion: The new role of glutathione

Abstract

Several methods, such as dilution, ion exchange, and bioaugmentation, have been tried to improve anaerobic digestion (AD) process performance under ammonia stress. Herein, a new strategy for improving AD under ammonia pressure by regulating microbiome and enzyme to enhance volatile fatty acids (VFAs) bioconversion was reported. Under ammonia stress, the methane yield was raised by 41.7% with glutathione addition (5 mg/g VS) during long-term AD of food waste. This glutathione-induced improvement was found not due to the mitigation of proton imbalance and potassium depletion or the elimination of excessive reactive oxygen species. Interestingly, the ammonia-stressed bioconversions of propionate and butyrate → acetate → methane and the cell viability were remarkably enhanced in the presence of glutathione. Further integrated metagenomic and metaproteomic analyses revealed that the key microbiota (i.e., syntrophic acetogenic taxa and their assistant bacteria and acetotrophic methanogens) related to the above biotransformations were enriched. Meanwhile, the expressions of vital proteins (such as RNA polymerase subunit α, ribosomal protein L25, and iron adenosine triphosphate binding cassette transporter substrate-binding protein) involved in enzyme synthesis and catalyzing the bioconversions above were significantly upregulated. The reported new role of glutathione on regulating functional microbiome and enzyme offered an alternative strategy for improving AD performance under high ammonia condition.