Deep Shotgun metagenomic and 16S rRNA analysis revealed the microbial diversity of lactic acid bacteria in traditional fermented foods of eastern Hainan, China

The eastern part of Hainan, China, has a flat terrain and a suitable climate with abundant sunshine and rain. This unique environment makes the tropical microbial resources of natural fermented food unique and rich. Therefore, we combined Shotgun metagenomic sequencing, 16S rRNA sequencing and pure culture technology to analyze the microbial diversity, microbiota composition, species differences and correlation of 30 traditional fermented food samples collected from Wenchang, Qionghai, Wanning and Lingshui in the eastern part of Hainan province, and isolated, identified and preserved the microorganisms in them. The results showed that the microbial community structure differs significantly between samples from different regions and between different substrates. The alpha diversity of microorganisms in traditional fermented foods in the Wanning area was higher than those of the other three areas. The beta diversity indicated that the microbiota structural difference between Wanning and Qionghai was smaller. This is consistent with the fact that the precipitation in the Wanning area is the highest and similar to that of Qionghai. The alpha diversity of microorganisms was the highest in fermented vegetables, followed by fermented grains, and the lowest in fermented seafood. Beta diversity showed that the microbiota composition of fermented grains and fermented vegetables is very similar, but that of fermented seafood is significantly different. The results of microbiota structural analysis showed that firmicutes and proteobacteria are the dominant bacterial phyla, and Lactobacillus plantarum and Lactobacillus fermentum are the dominant species in traditional fermented foods in eastern Hainan. Lactic acid bacteria are the dominant species in traditional fermented foods from the eastern Hainan region of China, regardless of the substrate used in fermentation. According to the microbial functional characteristics, the microbial metabolism and biosynthesis pathways in traditional fermented foods in Hainan tend to be active. In addition, combined with pure culture technology, we isolated, identified and preserved 342 lactic acid bacteria strains from traditional fermented food in eastern Hainan province. This study helped us understand the different characteristics of microbial communities in tropical southern China and supplement the Lactobacillus species resource pool in tropical southern China. Moreover, it provided new insights and directions for the development and utilization of fermented foods.