Metaproteomics reveals protein composition of multiple saccharifying enzymes in nongxiangxing daqu and jiangxiangxing daqu under different thermophilic temperatures

Abstract

Summary Daqu provides hydrolytic enzymes that saccharifying the macromolecular carbohydrate in fermenting grains. The process of saccharification is the premise of Baijiu production. But little is known about the protein composition associated with the activity of saccharifying enzymes in daqu. This study investigated related proteins between nongxiangxing daqu and jiangxiangxing daqu by metaproteomics. We present that the amylase system (α‐amylase, glucoamylase and α‐glucosidase) and cellulase system (cellobiohydrolases, endoglucanase and β‐glucosidase) are regarded as the main saccharifying enzymes. Combined with protein‐based taxonomic annotation, the key proteins involving in amylase system were mainly from Kroppenstedtia, Lichtheimia, Byssochlamys and Thermomyces, while Thermoascu contributed the most to cellulase system. Moreover, it was found that the up‐regulated amylase proteins at thermophilic fermentation period in jiangxiangxing daqu in comparison with nongxiangxing daqu were affiliated to Aspergillus, Rhizomucor, Byssochlamys and Thermomyces, along with Thermoascu contributing to cellulase system. These findings will provide clues for improving saccharification efficiency in Baijiu production.

Difference of microbial community and gene composition with saccharification function between Chinese nongxiangxing daqu and jiangxiangxing daqu

“…Liquefaction power was defined as the mass (g) of soluble starch liquefied for 1 h per gram of sample at 40 °C. An assay of enzymatic properties was completed in our previous study 18 …”

“…A previous study observed that there was a significant difference in saccharification capacity among different types of daqu 17 . Additionally, our previous study showed that the thermophilic temperature had an important effect on expression and activity of enzymatic proteins with saccharification function during daqu fermentation 18 . However, there are few reports regarding the difference in microbial enzymatic genes among different types of daqu .…”

Integrated multi‐omics approaches to understand microbiome assembly in Jiuqu, a mixed‐culture starter

“…Wheat Qu is widely used to make Chinese rice wine, whose process includes six main steps: wheat crushing, wetting the material with water, starter-treading and shaping, culturing in rooms, ventilating and drying, and storage (Zhang et al, 2019a). Compared with Daqu, wheat Qu has a relatively simple microbiota structure (Zhang et al, 2022).…”

“…A total of 2152 proteins were found to be associated with 273 fungal genera, most of which were related to carbohydrate metabolism and genetic information processing. Recently, Xia et al (2022) investigated the differences in saccharification enzyme proteins between MT-Daqu and HT-Daqu using label-free quantitative metaproteomics. They found that the upregulated amylase proteins in HT-Daqu compared to MT-Daqu in the high-temperature incubation stage were associated with Aspergillus, Rhizomucor, Byssochlamys, and Thermomyces, with Thermoascu contributing cellulase.…”

“…As described above, metagenomics, metatranscriptomics, metaproteomics, and metametabolomics have their own characteristics (Figure 7). Metagenomics can not only provide distinct insight into the specific taxonomic classification of sequences in Jiuqu at the species level, especially, the identification of unculturable microbes but also globally reveal details of the microbiota assembly and potential gene function F I G U R E 7 Integrated multi-omics strategy for dissecting the microbiome of Jiuqu (Fan, Huang, et al, 2020;Yang et al, 2021b;Zhang et al, 2022). Metatranscriptomics can further explain the structure and function of live microbes and their important genes in Jiuqu based on the global expression of mRNA in the microbiome (Yi et al, 2019).…”