Identification and functional prediction of the key fungus of Hongxinqu for Light-flavor Baijiu brewing

Hongxinqu is an indispensable kind of Daqu for brewing the famous Light-flavor Baijiu, but the key fungus that forms a red line in the central part of Hongxinqu is still unclear. In this study, the central part of four pieces of Hongxinqu bricks were taken as samples, and their fungal communities were analyzed by high-throughput sequencing technology. It was found that Ascomycota, which accounted for about 99% of all samples, was the most dominant phylum; at the genus level, Thermoascus represented 98% in FH1, while slightly decreased in the remaining three samples, but still maintaining about 76.48%–84.06%; therefore, Thermoascus was the dominant genus. Furthermore, four strains (QH-1, QH-3, QH-4, and FH-7) isolated from the central part of Hongxinqu bricks were found to produce red pigment, and all of the four strains were identified as Thermoascus aurantiacus. And it was found that these four strains could produce amylase and esterase, which meant that Thermoascus aurantiacus could degrade starch to reducing sugar and produce some aroma components of Baijiu. Identifying the key microorganism that produced the red line in the central part of Hongxinqu bricks will help to optimize the process parameters and improve the quality of Hongxinqu.