Microbial-driven mechanisms of arsenic methylation during Chinese rice wine fermentation

Arsenic (As) may be a potential contaminant in Chinese rice wine. The methylation of As, which was evaluated as a possible detoxification mechanism to solve this issue. In this study, we simulated Chinese rice wine fermentation under laboratory conditions to explore As methylation behavior. The total As content of Chinese rice wine decreased by 68.6 % after fermentation. As species were transformed during fermentation; inorganic arsenic (iAs) was converted to methylated As; iAs decreased by 73.29 %, and the dimethylarsenic acid (DMA) percentage increased from 4.4 % to 19.9 %. We found that the As methylation gene (arsM) was ubiquitous in Chinese rice wine. Correlation analysis showed that physicochemical properties determined arsM abundance and DMA content during fermentation. The microbial As methylation pathway was summarized based on the annotated As functional genes from the Kyoto Encyclopedia of Genes and Genomes database. Higher relative abundances of glutathione S-transferase and arsC promoted the formation of more trivalent As substrates and further promoted methylation behavior for As detoxification during fermentation. According to the microbial arsM contribution analysis, Mycobacteroides, Rhizopus, and Jimgerdemannia were the primary As methylation microorganisms in Chinese rice wine. These results highlighted the specific As methylation process during fermentation, which could improve the control of As contamination in Chinese rice wines.