酱香型白酒发酵过程中核心酵母的鉴别及其功能

Identification of core yeasts and their functions in the fermentation process of Maotai-flavor Baijiu

摘要:

【背景】酵母是酱香型白酒发酵过程中最重要的微生物，但酵母群落中核心酵母的种类和功能尚不清晰。【目的】通过探索酱香型白酒发酵微生物群落中核心酵母的种类和功能，为揭示酱香型白酒酿造机制以及提升白酒品质提供理论支撑。【方法】联合使用未培养(内转录间隔区扩增子和宏转录组高通量测序技术)和可培养(菌种筛选和模拟发酵实验)技术对酱香型白酒发酵过程中核心酵母的结构和功能进行定性和定量分析。【结果】内转录间隔区扩增子和宏转录组测序结果显示，酱香型白酒发酵过程中涉及10个属的酵母微生物，其中在发酵过程中平均相对丰度大于0.2%的酵母有13种，有2种核心酵母分别为库德威兹氏毕赤酵母(Pichia kudriavzevii)和粟酒裂殖酵母(Schizosaccharomyces pombe)。在发酵过程中，P. kudriavzevii占总量的89%以上，Schi. pombe表达了占总量21%以上的功能基因。模拟发酵实验结果显示P. kudriavzevii在酵母群落中发挥耐受乳酸积累的作用，而Schi. pombe在酵母群落中发挥耐受乙醇积累的作用，这两种作用保证了酱香型白酒发酵过程中酵母群落的结构和功能的稳定性。【结论】P. kudriavzevii和Schi. pombe是酱香型白酒发酵过程中的优势酵母，这两种酵母在生产中发挥了各自不同的作用。本研究进一步加深了核心酵母对于整个生产过程贡献的认识，有助于研究者认识到白酒发酵过程中对核心微生物进行调控的重要性。

Abstract:

[Background] Yeasts are the most important microbes in Maotai-flavor Baijiu production. However, the structures and functions of core yeasts in the fermentation microbiota are unclear. [Objective] To reveal the fermentation mechanism of the Baijiu-making process and improve the product quality, we illustrated the structures and functions of core yeasts in fermentation microbiota. [Methods] Culture-independent (internal transcribed spacer amplicons and metatranscriptomics sequencing) and culture-dependent (strain selection and simulated fermentation experiments) technologies were used to analyze the structural change of yeast microbiota and function of core yeasts in the fermentation process of Maotai-flavor Baijiu production. [Results] Results of amplicons and metatranscriptomics showed that yeast in the fermentation process classified to 10 genera. We selected 13 core structure species (relative abundance>0.2%) of yeast microbiota and identified 2 core yeasts including Pichia kudriavzevii and Schizosaccharomyces pombe. In the fermentation process, the relative abundance of P. kudriavzevii had more than 89% of the total microbes in the yeast microbiota. Meanwhile, Schi. pombe expressed more than 21% of the total functional genes in the yeast microbiota. Moreover, the results of the simulated fermentation experiments showed that P. kudriavzevii could tolerate lactic acid accumulation and Schi. pombe could tolerate ethanol accumulation in the yeast microbiota. The effects of two core yeasts ensure the stability of Baijiu production during the fermentation process. [Conclusion] P. kudriavzevii and Schi. pombe are the dominant yeasts in the fermentation process of Maotai-flavor Baijiu production. These two yeasts play different roles during fermentation. Our research further deepened our knowledge about the contribution of core yeasts for fermentation process. It also makes researchers recognize the importance of the regulation of core microbes during Baijiu production.