Abstract: The microbial community succession of fermented mutton sausage during natural fermentation was determined using metagenomic technology, and the metabolic pathways of volatile flavor substances and the microorganisms and enzymes involved in the metabolism of volatile flavor substances were annotated and analyzed by using the Evolutionary Genealogy of Genes: Non-supervised Orthologous Groups (eggNOG) database, the Kyoto Encyclopedia of Genes and Genomes (KEGG) database and the Carbohydrate-Active Enzymes (CAZy) database. The results revealed that Haemophilus influenzae, Staphylococcus aureus, and Oenococcus oeni were the dominant species during the fermentation process, and the relative abundance of Staphylococcus saprophyticus and Staphylococcus equorum reached a peak of 16.52% and 10.53% after 14 days of fermentation, respectively. Among the samples fermented for 0, 5, 14 and 26 days, the samples fermented for 5 days had the highest number of genes annotated. Carbohydrate metabolism and amino acid metabolism were the most annotated metabolic pathways, and glycosidohydrolase and glycosyltransferase were the most abundant enzymes involved in carbohydrate metabolism. Totally 167, 217 and 92 genes encoding enzymes involved in amino acid metabolism, carbohydrate metabolism and fatty acid metabolism were found, respectively. The enzymes participating in the three metabolic pathways were mainly annotated in Staphylococcus, Leuconostoc, Pseudomonas, Psychrobacter, and Vibrio. The abundance of most of the enzymes attained a maximum after 14 days of fermentation. The results obtained in this study provide a significant reference for the analysis of the dynamic changes of microorganisms and the formation mechanism of volatile flavors in fermented mutton sausage.

Key words: mutton sausage; metagenomics; microbial diversity; volatile flavor; metabolic pathway; functional gene