Stabilization of jiuyao quality for huangjiu brewing by fortifying functional strains based on core microbial community analysis

Jiuyao as a generally small saccharifying and spontaneously fermenting starter is indispensable for huangjiu brewing. However, jiuyao currently in use is facing a major challenge of standardized manufacturing because its open operating environment and rather primitive operations. This study provided a stead manufacturing procedure for jiuyao by controlling the processing parameters. Saccharomycopsis fibuligera and Rhizopus micro-sporus were revealed as the core functional species related to starch-degrading enzyme activities with single-molecule real-time (SMRT) sequencing. Two strains with high starch-degrading abilities were successfully iso-lated and identified as Saccharomycopsis fibuligera CY2111 and Rhizopus microsporus SM4. Meanwhile, the environmental fermentation parameters of jiuyao were optimized to enhance enzyme activities. The glucoa-mylase and alpha-amylase activities of fortified jiuyao with strain CY2111 and SM4 were 3.07 and 3.15 times that traditional jiuyao, respectively. Moreover, the alcohol content increased by approximately 7.5% when fortified jiuyao was used for huangjiu brewing. The flavor profiles determined by gas chromatography-mass spectrometry indicated there was no significant difference in the key aromas between the huangjiu fermented with fortified jiuyao and that of traditional jiuyao. Further, fortified jiuyao produced more pleasant esters in huangjiu such ethyl isovalerate, isoamyl acetate, and ethyl caprylate. Combined with the sensory evaluation, huangjiu fer-mented with fortified jiuyao presented stronger fruity aroma. These results demonstrated that careful fermen-tation settings combined with biofortification technology were feasible to improve jiuyao quality, thus promoting huangjiu flavor. Taken together, it provided scientific guidance to improve traditional handcrafting and scale the production of jiuyao under controllable fermentation.