Bacteria Responsible for Producing Biogenic Amines in Sufu Raw sequence reads

Biogenic amines (BAs) are frequently identified with harmful levels in sufu products. However, the microorganisms and mechanisms responsible for BA production in sufu are less documented. In this study, sufu samples were randomly obtained from various region of China, and putrescine , tyramine , and histamine were quantitated as the most abundant BAs. Based on the metagenome sequencing, the abundances and diversities of genes encoding the critical enzymes in BA production were acquired. The results showed that genes encoding arginine decarboxylase (adcA gene), ornithine decarboxylase (odcA), tryptophan decarboxylase (tdcA) and histidine decarboxylase (hdcA) were the predominant amino acid decarboxylase genes in sufu microbial communities. Furthermore, the 34 metagenome-assembled genomes (MAGs) were recruited (with average completeness of 92.04% and contamination rate of 2.25%); among them, 23 MAGs classified in 17 different genera, carried genes involved in BA production. Genetic analysis of MAGs indicated genus affiliated with Enterococcus, Lactobacillus, and Lactococcus were the major histamine-synthesizing bacteria, and tyrosine may be utilized by Bacillus, Chryseobacterium, Kurthia, Lysinibacillus, Macrococcus, and Streptococcus to product tyramine. The critical species involved in two putrescine producing pathways were also explored. In the ornithine decarboxylase pathway, Lactobacillus and Veillonella are predicted as the main performers, whereas Sphingobacterium and unclassified Flavobacteriaceae are the dominant executors in agmatine deiminase pathway in putrescine production. The present study not only helped to explain the BAs formation mechanism in sufu, but also provided targeted bacteria to control the BAs in fermented soybean products.