A research team has identified a brand-new bacterial species from the fermented grains used in Chinese baijiu production. Named Aneurinibacillus baijiui sp. nov., the newly discovered strain (REN35ᵀ) plays a notable role in producing diverse flavor compounds that contribute to the aroma complexity of baijiu.
The bacterium was isolated from baijiu grains collected in Sichuan Province and characterized using a polyphasic taxonomic approach. The strain is Gram-positive, rod-shaped, motile, and grows optimally at 30°C, pH 7, and low salinity (0.5% NaCl). Comparative 16S rRNA analysis revealed only 97.6% similarity with its closest relatives—Aneurinibacillus migulanus and A. aneurinilyticus—well below the 98.7% threshold for species identification. Genome-based ANI (70.0–75.9%) and dDDH (18.2–20.9%) values further confirmed that REN35ᵀ represents a distinct species.
Chemotaxonomic analysis highlighted iso-C15:0 and iso-C16:0 as major fatty acids, with MK-7 as the dominant respiratory quinone. The strain also carries biosynthetic gene clusters for secondary metabolites, including betalactones, proteusins, siderophores, and a Type III polyketide synthase.
One of the most significant findings is the bacterium’s ability to generate 38 different volatile flavor compounds during fermentation. GC-MS analysis identified key molecules such as dimethyl disulfide, 2,6-dimethylpyrazine, acetophenone, ethyl formate, and 5-hydroxymethylfurfural. These compounds contribute essential notes—garlic-like sulfur aromas, nutty pyrazines, fruity esters, and sweet aldehydes—that define the sensory identity of baijiu.
Taken together, the phenotypic, genomic, and chemotaxonomic evidence support the establishment of Aneurinibacillus baijiui sp. nov., with REN35ᵀ designated as the type strain. This discovery expands the known microbial diversity involved in baijiu fermentation and highlights the crucial role of bacteria in shaping the traditional beverage’s aroma and flavor profile.
Reference
Zhang, R., Li, Y.M., Gu, H.Y. et al. Isolation and Characterization of Aneurinibacillus baijiui sp. nov., a Novel Bacterial Species from Fermented Grains of Baijiu Capable of Producing Diverse Flavor Compounds. Microbiology 94, 913–921 (2025). https://doi.org/10.1134/S0026261725601629
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