Fermented foods often have attractive flavor characteristics to meet various human demands. An ever-challenging target is the production of fermented foods with equal flavor profiles outside the product's origin. However, the formation of geography-dependent flavor in high-complexity fermentations remains poorly understood. Here, taking Chinese liquor (baijiu) fermentation as an example, we collected 403 samples from 9 different locations in China across a latitude range of 27°N to 37°N. We revealed and validated the geography-dependent flavor formation patterns by using culture-independent (metabolomics, metagenomics, and metatranscriptomics) and culture-dependent tools. We found that the baijiu microbiomes along with their metabolites were flavor related and geography dependent. The geographical characteristics were determined mainly by 20 to 40 differentiated chemical markers in metabolites and the latitude-dependent fungal structure of the microbiome. About 48 to 156 core microbiota members out of 735 bacterial genera and 290 fungal genera contributed to the chemical markers. The contributions of both fungi and bacteria were greater than those from either bacteria or fungi alone. Representatively, we revealed that dynamic interdependent interactions between yeasts and Lactobacillus facilitated the metabolism of heterocyclic flavor chemicals such as 2-acetylpyrrole, 2,3,5-trimethylpyrazine, and 2-acetylfuran. Moreover, we found that the intraspecific genomic diversity and microbial structure were two biotic factors that contributed to dynamic microbiome assembly. Based on the assembly pattern, adjusting the composition and distribution of initial species was one option to regulate the formation of diverse flavor characteristics. Our study provided a rationale for developing a microbiome design to achieve a defined flavor goal. IMPORTANCE People consume many spontaneously fermented foods and beverages with different flavors on a daily basis. One crucial and hotly discussed question is how to reproduce fermented food flavor without geographical limitations to meet diverse human demands. The constantly enriched knowledge of the microbial contribution to fermented flavor offers valuable insights into flavor biotechnological development. However, we still have a poor understanding of what factors limit the reproduction of fermented flavor outside the product's origin in high-complexity spontaneous fermentations. Here, taking baijiu fermentation as an example, we revealed that geography-dependent flavor was contributed mainly by fungus-bacterium cooperative metabolism. The distinct initial microbial composition, distribution, and intraspecific genomic diversity limited reproducible microbial interactions and metabolism in different geographical areas. The abundant microbial resources and predicted fungus-bacterium interactions found in baijiu fermentation enable us to design a synthetic microbial community to reproduce desired flavor profiles in the future.
Keywords: Chinese liquor; flavor biotechnology; geography-dependent flavor; microbial community; microbial interaction; spontaneous fermentation.