Abstract:[Background] Thermophilic strains are ubiquitous in the brewing environment of Baijiu and are a microbial group indispensable for the brewing of Baijiu. [Objective] To isolate and identify thermophilic strains in the samples collected from the brewing environment of Baijiu and characterize the growth of the strains, thereby laying a theoretical foundation for the application of the strains in the production of Baijiu. [Methods] Gradient dilution was carried out for the samples of Jiuqu (starter), Jiupei (fermented grains), and Jiuzao (distilled grains), respectively. The samples with suitable dilution factors were then selected and coated on the Luria-Bertani, yeast extract peptone dextrose, and potato dextrose agar media, respectively. The plate streaking method was employed to isolate the strains. [Results] A total of 22 strains of thermophilic bacteria and 18 strains of thermophilic fungi were screened out. Among them, 4 species of bacteria and 4 species of fungi with distinct colony morphology were selected and identified by morphological observation, physiological and biochemical tests, and phylogenetic analysis. The four species of bacteria were identified as Streptomyces albulus, Bacillus subtilis, B. amyloliquefaciens, and B. rugosus, and the four species of fungi were identified as Rhizomucor pusillus, Thermomyces lanuginosus, Thermoascus crustaceus, and Malbranchea cinnamomea. It is worth noting that B. rugosus and M. cinnamomea had not been reported in the research on Baijiu. The eight species showcased differences in the growth temperature range, pH range, and NaCl tolerance. [Conclusion] We screened out, identified, and characterized the growth of four species of thermophilic bacteria and four species of thermophilic fungi, which provided data support for studying the roles and applications of these microorganisms in the brewing of Baijiu.
