Exploring the contribution of temperature-adapted microbiota to enzyme profile of saccharification in Daqu using metagenomics and metaproteomics

Temperature is a critical factor that influences the microbiota in Daqu, which provides essential enzymes for the saccharification process in Baijiu (Chinese liquor) production. However, the relationship between temperature-adapted microbiota and saccharification properties of Daqu remains unclear. In this study, a profile of 23 major saccharifying enzymes and 40 responsible genera was obtained from the metagenomic data of medium- and high-temperature Daqu (MT- and HT-Daqu). The high-temperature pattern (65 °C) primarily affected the saccharification potential of Daqu by promoting Bacillales (fold-change: 0.25–0.75), whereas inhibiting Lactobacillales (fold-change: 3.80–5.60) and Mucorales (fold-change: 5.65–7.09). Eurotiales only exhibited a slight increase (fold-change: 1.01–1.24) to low-temperature pattern (56 °C). Metaproteomic analysis further revealed a notable contribution of Eurotiales in facilitating saccharification. Amylolytic enzymes were primarily derived from Eurotiales species (Byssochlamys spectabilis, Monascus purpureus, Rasamsonia emersonii, and Thermomyces lanuginosus) and one Mucorales species, Lichtheimia romasa. Cellulolytic enzymes were produced by Thermoascus aurantiacus and Paecilomyces sp. Among them, L. romasa was the principal contributor under the low-temperature pattern. Whereas, in HT-Daqu, B. spectabilis, M. purpureus, and T. lanuginosus were the major contributors, as L. romasa is susceptible to higher temperatures. This study offers valuable guidance for targeted optimization of industrial production.