To reveal the brewing mechanism of Sichuan Xiaoqu liquor, microbial communities in Xiaoqu, a saccharification and fermentation agent, were characterized using microbial isolation and identification techniques, MiSeq high-throughput sequencing and bioinformatics. From Xiaoqu commonly used in three different regions (Dazhu, Pengzhou and Hubei) in China, three yeast strains and seven moulds were isolated and identified. In addition, 17 bacteria and seven fungi were detected by high-throughput sequencing. In Xiaoqu from Pengzhou (Huaxi Xiaoqu), the dominant species were Weissella cibaria (85.52%) and Rhizopus stolonifer (94.98%). On the other hand, W. cibaria (17.64%), Staphylococcus sp. (53.17%), Saccharomyces cerevisiae (43.33%), and Candida fennica (38.52%) were preponderant in Xiaoqu from Dazhu (Sichuan Dazhu Xiaoqu). Finally, Xiaoqu from Hubei consisted mostly of W. cibaria (29.64%), uncultured Empedobacter bacteria (32.60%), R. stolonifer (18.90%), Cunninghamella bertholletiae (67.41%) and S. cerevisiae (10.95%). Clearly, the bacterial community was relatively more complex than the fungal community. However, the fungal content in Xiaoqu of the three different regions was consistent. The results indicate that different flavours from different regions may result mainly from the bacterial and fungal diversity in their Xiaoqu.

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On the basis of single-factor test, we conducted optimization study on the three major factors (material moisture content, cultivation time, temperature) that affect the production of purebred Monascus spores through orthogonal trial. The results show that, in the trial-level range, moisture content of materials and cultivation time have larger effect on the test results, while the cultivation temperature has little effect. The optimum conditions in preparation of purebred Monascus seed koji are: 60% moisture content of materials, 5 d cultivation time, 35°C cultivation temperature, 0.1 mL inoculation, 10 g filling and 0.2% lactic acid. To verify this test scheme, ultimately the number of spores produced by Monascus is 3.35×10 7 /g.

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