The ester production capacity of Pichia kudriavzevii based on functional annotation of genes.

Esters were identified as the primary volatile flavor compounds in Chinese Baijiu, exerting a significant influence on its quality and aroma. This study focused on the yeast strain Pichia kudriavzevii, renowned for its high capacity to produce esters. Whole genome sequences were annotated and analyzed using the GO, KEGG, KOG, CAZy, and Pfam databases to determine the genetic basis underly the enhanced ester production capacity. Results showed that P. kudriavzevii gene function was concentrated in biosynthetic capacity, metabolic capacity, amino acid translocation capacity, glycoside hydrolysis capacity and transfer capacity. Additionally, acyltransferase and kinase were predicted as active sites contributing to P. kudriavzevii high ester production. We further compared the volatile composition differences between P. kudriavzevii and Saccharomyces cerevisiae through Headspace solid-phase microextraction-gas Chromatography-mass spectrometry (HS-SPME-GC-MS), revealing P. kudriavzevii produced 3.5 times more esters than S. cerevisiae. Overall, our findings suggest that P. kudriavzevii had potential applications in the Baijiu brewing industry.

Correlational analysis of physicochemical indexes, microbial communities, and volatile components in light-flavor Daqu from north and south regions of China.

Daqu is of great significance to the brewing process of Baijiu, and there are variations in the light-flavor Baijiu Daqu in different regions. However, few studies have been conducted on light-flavor Daqu from the north and south regions of China. In this study, the physicochemical indices, volatile flavor components, and microbial community structure of two types of Daqu from the north and south regions of China were comparatively analyzed. The study findings reveal that Daqu originating from the southern region of China (HB) exhibits superior moisture content, acidity, starch content, and saccharification power. In contrast, Daqu from the northern region of China (SX) displays higher fermentation, esterification, and liquefaction power. The analysis of the microbial community structure revealed that HB was dominated by Bacillus, Kroppenstedtia, Saccharomycopsis, and Thermoascus, while SX was dominated by Bacillus, Prevotella, and Saccharomycopsis. The analysis detected a total of 47 volatile components in both HB Daqu and SX Daqu. The volatile components of pyrazine were significantly more abundant in HB Daqu than in SX Daqu, while alcohol compounds were more prominent in SX Daqu than in HB Daqu. In addition, the RDA analysis established a correlation between dominant microorganisms and volatile components. Cyanobacteria, Fusobacteriota, Ascomycota, Blastocladiomycota, Basidiomycota, and Mucormyce exhibited positive correlations with a significant proportion of the key volatile compounds. This study establishes a scientific foundation for improving the quality of light-flavor Daqu liquor in different regions of China.