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Rice wine koji is made from "ChengQu" as the parent species and is prepared by enriching microorganisms in the environment, which plays a decisive role in the formation of quality rice wine. This study explored the microbiome of 18 rice wine koji collected from Xiaogan, Fangxian, Hubei, Dazhou, and Sichuan and analyzed the sensory quality and microbiome of rice wine made with rice koji as a fermentation agent. Although our results showed that there were large differences in microbial communities and functions in rice wine koji, samples from the same region had a higher similarity, and the closer the distance, the higher the similarity. Five suspected new species (Lactococcus sp., Weissella sp., Lactobacillus sp., and Acetobacter sp.) were discovered by ultra-high-depth metagenomic sequencing; their functional maps and phase correlation analysis showed that they contributed positively to the aroma of rice wine. The sensory quality and microbial community structure of rice wine fermented with different rice wine koji have obvious differences, consistent with the structural difference of microorganisms in rice wine koji in different regions. These findings indicate that rice wine koji directly determines the structure of microorganisms in rice wine and directly or indirectly affects the sensory quality of rice wine. • Microbiome and quality of six Xiaogan, six Fangxian and six Dazhu rice wine koji were analyzed. • Samples from adjacent regions shared higher similarity in microorganisms and product quality. • Five novel species of Lactococcus sp., Weissella sp., Lactobacillus sp., and Acetobacter sp. were discovered. • Rice wine koji played significant role in shaping rice wine microbiome and thus flavor quality. • Ultra-high depth metagenomic sequencing was necessary to make reliable conclusions. [ABSTRACT FROM AUTHOR]

Rice wine, a traditional fermented alcoholic beverage in China, is produced with grains such as rice, which are fermented with saccharifying starter-koji. Its flavor quality is closely associated to the starter culture-koji, which is made by mixing botanical materials with high-class glutinous rice in certain ecological context. However, there are few reports on the microbial community structure of rice wine koji. In this paper, bacterial community structures of rice wine koji were analyzed using 16S rRNA gene sequencing based on Illumina MiSeq high-throughput technology in 20 samples collected from Xiaogan area, Hubei province and Dazhu area, Sichuan province (10 from each area). We found rice wine koji flora mainly consisted of Weissella, Lactobacillus, Lactococcus, Bacillus, Enterococcus, and Cronobacter, with relative abundances of 29.49%, 10.93%, 8.85%, 4.75%, 1.16% and 1.15%, respectively, as well as an accumulative average relative abundance of 58.71%. They all belonged to Firmicutes and Proteobacteria—the two known dominant genus. Genus-level PCA (Principal component analysis) and OTU-level PCoA (Principal coordinates analysis) based on unweighted UniFrac distances showed that the bacterial community structure differed significantly between the samples from the 2 areas. 7 OTUs were detected in all samples, accounting for 4.4% of the total qualified assembly. Among the 7 OTUs, 3 OTUs were identified as Enterococcus, 2 OTUs were identified as Cronobacter, 1 OTU was identified as Bacillus and 1 OTU was identified as Alkaliphilus. Fifty-eight lactic acid bacteria (LAB) strains were isolated from the 20 koji samples with traditional microbial methods. Among them, Enterococcus faecium and Pediococcus pentosaceus were the dominant LAB isolates, with relative abundances of 51.72% and 31.03%. Despite the differences, a large number of shared bacteria were detected in samples from the two areas. [ABSTRACT FROM AUTHOR]