Manufactural impact of the solid-state saccharification process in rice-flavor baijiu production

Rice-flavor baijiu is a traditional Chinese liquor that is manufactured using a solid-state saccharification process. In the present study, we investigated the role of the process in making of rice-flavor baijiu using chemical and biological quantitative analysis approaches. More than 70% of starch in rice decomposed to glucose after saccharification. In addition, the number of fungal cells, saccharification activity, and lactic acid concentration increased. Rhizopus oryzae was identified as the major fungus proliferating under saccharification based on denaturing gradient gel electrophoresis analysis targeting the internal spacer transcribed region. Lactic acid bacteria were not detected by 16S rRNA gene-based next-generation sequencing analysis during saccharification. Conversely, R. oryzae, isolated from xiaoqu, exhibited a capacity to produce lactic acid. The results imply that the solid-state saccharification is essential not only for saccharification but also for the culture of R. oryzae, which promote saccharification activity and lactic acid production. We also investigated the most appropriate temperature for solid-state saccharification and 35°C was the optimum temperature for R. oryzae cultivation, enzyme production, and saccharification. The results could facilitate the efficient and stable manufacture of rice-flavor baijiu.