白酒酿造过程中Lactobacillus panis乳酸合成关键环境因子的鉴定

Identification of Key Environmental Factors of Lactic Acid Biosynthesis by Lactobacillus panis for Chinese Liquor Brewing

Lactobacillus panis是酱香型白酒酿造过程中主要产乳酸微生物。然而,不同环境因子对L.panis乳酸合成及乳酸合成途径关键基因的表达尚未有相关研究。作者分析了温度、乳酸、乙醇及葡萄糖4种不同的发酵过程相关的典型环境因子对L.panis乳酸产量的影响。结果表明,不同环境条件能够显著调节L.panis的生长和乳酸产量,且乳酸和乙醇是酿造过程中其乳酸合成的关键影响因素。当添加10.0 g/L乳酸后,L.panis的乳酸产量最高,达到12.3 g/L;当添加体积分数4.0%乙醇后,L.panis的乳酸产量最低,仅为7.2 g/L。使用实时荧光定量PCR方法对不同条件下L.panis乳酸合成相关基因的表达进行分析,结果表明添加乳酸能够显著上调包括编码L-乳酸脱氢酶和D-乳酸脱氢酶的ldhL和ldhD在内的乳酸合成基因的表达。然而,添加乙醇会导致L.panis乳酸合成相关基因的整体显著下调。分析调控乳酸合成的关键环境因素,对于白酒酿造过程中乳酸和酿造微生物群落调控及白酒质量控制具有重要意义。

Lactobacillus panis has been identified as the major lactic acid-producing bacterium in the fermentation of Maotai-flavor liquor.However,the effects of different environmental conditions on lactic acid metabolism and expression level of key genes in the lactic acid pathways of L.panis have not been studied.In this work,different environmental factors relevant to fermentation processes were selected,such as temperature,lactic acid,ethanol,and glucose concentrations.Results showed that under different environmental conditions,the growth and lactic acid yield of L.panis were significantly regulated.Lactic acid and ethanol were identified to be the key factors of lactic acid biosynthesis by L.panis.The maximum amount(12.3 g/L)of lactic acid was achieved when 10 g/L lactic acid was added to the growth medium.In contrast,the addition of 40 g/L ethanol reduced lactic acid production to 7.2 g/L,which was the lowest level among the different environmental conditions.Quantitative real-time PCR analysis of key genes involved in lactic acid metabolism with lactic acid supplementation showed that lactic acid addition significantly facilitated up-regulation of key gene for lactic acid synthesis,including ldhL and ldhD encoding L-lactic acid dehydrogenase and D-lactic acid dehydrogenase,respectively.However,their expression levels were down-regulated if ethanol added,implying a decreased metabolic flux through the lactic acid synthetic pathway.The analysis of key environmental factors determining lactic acid production of L.panis is of great significance for modulation of lactic acid synthesis during fermentation,and would also be useful for controlling the brewing microbial community and quality of the liquor.