Integrative Metagenomics–Metabolomics for Analyzing the Relationship Between Microorganisms and Non-volatile Profiles of Traditional Xiaoqu

Abstract

<i>Xiaoqu</i>, one of three traditional <i>jiuqu</i> in China, is a saccharifying and fermenting agent used in <i>Xiaoqu jiu</i> brewing, with different ingredient compositions and preparation techniques used in various regions. The yield and quality of <i>Xiaoqu jiu</i> are significantly affected by the metabolites and microbiota of <i>Xiaoqu</i>; however, the associated relationship remains poorly understood. This study aimed to analyze this relationship in three typical traditional <i>Xiaoqu</i> from the Guizhou province in China. The non-volatile metabolites of <i>Xiaoqu</i> were detected using gas chromatography time-of-flight mass spectrometry, whereas the classification and metabolic potential of the microbiota were investigated using metagenomic sequencing. Results show that Firmicutes, Proteobacteria, and Actinobacteria represent the dominant bacterial phyla, with <i>Lactobacillus, Bacillus, Acinetobacter, Leuconostoc</i>, and <i>Weissella</i> found to be the dominant bacterial genera. Meanwhile, Ascomycota, Mucoromycota, and Basidiomycota are the dominant fungal phyla with <i>Aspergillus, Saccharomyces, Pichia, Rhizopus</i>, and <i>Phycomyces</i> being the predominant fungal genera. Functional annotation of the microbiota revealed a major association with metabolism of carbohydrates, cofactors, and vitamins, as well as amino acids. A total of 39 significantly different metabolites (SDMs) were identified that are involved in 47 metabolic pathways, primarily that of starch and sucrose; glycine, serine, and threonine; glyoxylate and dicarboxylate; pyruvate; as well as biosynthesis of pantothenate and CoA. Further, based on Spearman's correlation analysis, <i>Aspergillus, Saccharomyces, Lactobacillus, Acetobacter, Weissella, Pantoea, Desmospora</i>, and <i>Bacillus</i> are closely correlated with production of physicochemical indexes and SDMs. Moreover, the metabolic network generated for the breakdown of substrates and formation of SDMs in <i>Xiaoqu</i> was found to primarily center on the metabolism of carbohydrates and the tricarboxylic acid cycle. These results provide insights into the functional microorganisms and metabolic patterns present in traditional Guizhou <i>Xiaoqu</i> and might guide researchers in the production of stable and efficient <i>Xiaoqu</i> in the future.