浓香型白酒发酵过程微生物合成正丙醇途径解析

Microbial n-propanol synthesis during Luzhou-flavor liquor fermentation

【目的】揭示浓香型白酒窖内发酵过程与正丙醇合成相关的微生物和代谢途径。【方法】通过对浓香型白酒窖内发酵过程酒醅中微生物的宏转录组进行分析,解析与正丙醇合成相关的微生物和代谢途径,并验证相关微生物合成正丙醇的能力。【结果】浓香型白酒窖内发酵过程中有3条可能的酒醅微生物合成正丙醇的途径。真菌主要通过2-甲基苹果酸代谢途径和苏氨酸代谢途径合成正丙醇,细菌则主要通过丙酸代谢途径合成并参与苏氨酸代谢途径。宏转录组测序分析表明,这3条途径对白酒窖内发酵过程正丙醇的合成与积累均有贡献,并且微生物通过这3条途径合成正丙醇的时期和能力存在较大差异。此外,对分离自酒醅的酵母和乳酸菌合成正丙醇能力分析发现,它们均与浓香型白酒窖内发酵过程正丙醇的合成有关。【结论】本研究揭示了浓香型白酒窖内发酵过程中正丙醇合成相关的微生物和代谢途径,为阐明白酒发酵过程中正丙醇的形成机制奠定了理论基础。

[Objective]To reveal the metabolic pathways of n-propanol synthesis and corresponding microorganisms during Luzhou-flavor liquor fermentation.[Methods]The microorganisms and metabolic pathways related to the synthesis of n-propanol were analyzed by metatranscriptome analysis,and the capability of corresponding microorganisms to synthesize n-propanol was investigated.[Results]Three possible n-propanol synthetic pathways were discovered during Luzhou-flavor liquor fermentation.All of them contributed to the synthesis of n-propanol based on the transcriptome analysis.However,the time and capability of microorganisms to synthesize n-propanol through these pathways were different.Fungi synthesized n-propanol mainly through citramalate pathway and threonine metabolic pathway,whereas bacteria synthesized n-propanol through propanoate pathway and partial threonine metabolic pathway.Moreover,yeast strains and lactic acid bacteria isolated from fermented grains were confirmed to be corresponding to the synthesis of n-propanol during Luzhou-flavor liquor fermentation.[Conclusion]Discovery of metabolic pathways of n-propanol synthesis and corresponding microorganisms during Luzhou-flavor liquor fermentation help to understand the formation mechanism of n-propanol in the process of Chinese liquor fermentation.