白酒窖泥中乳酸菌分离鉴定及其发酵产挥发性风味物质比较

Isolation and Identification of Lactic Acid Bacteria from Mud of Baijiu and Comparison of Fermented Volatile Flavor Compounds

从白酒窖泥中分离得到11株乳酸菌,经16S rDNA基因序列同源性分析,鉴定为1株短乳杆菌、1株鼠李糖乳杆菌、2株干酪乳杆菌和7株铅黄肠球菌。分析了11株菌MRS培养基发酵产乳酸性能,结果表明:乳酸产量与菌群生长呈正相关,鼠李糖乳杆菌L9、干酪乳杆菌L10与L11发酵液乳酸含量较高,分别为15.74、15.58、14.74 g/L。4株代表菌相同条件下发酵高粱培养液产挥发性风味组分,共有物质13种,包含了白酒中重要香气成分:乙酸、己酸、乙酸苯乙酯和苯乙醇,且乙酸、己酸相对含量较高。各菌产可挥发性组分差异明显,相对含量较高的化合物种类为:短乳杆菌L5产烷烃类化合物(27.91%),铅黄肠球菌L8产醇类化合物(43.14%),鼠李糖乳杆菌L9产酯类(7.35%)、酮类(3.61%)和吡嗪类(3.3%)化合物,干酪乳杆菌L11产酸类(27.98%)和芳香类(5.96%)化合物。仅有短乳杆菌L5产四甲基吡嗪,短乳杆菌L5和铅黄肠球菌L8可明显产乙醇,鼠李糖乳杆菌L9和干酪乳杆菌L11产3-羟基-2-丁酮。这些物质对白酒风味和口感有重要影响。研究显示,窖泥中各种乳酸菌特征不一,对白酒酿造有不同影响。本研究旨在为进一步挖掘白酒酿造功能微生物、拓展乳酸菌的应用提供理论依据。

11 strains of lactic acid bacteria were isolated from mud of Baijiu and identified by 16 S rDNA gene sequence homology analysis. There were 1 strain of Lactobacillus brevis, 1 strain of Lactobacillus rhamnosus, 2 strains of Lactobacillus casei and 7 strains of Enterococcus casseliflavus. Lactic acid production was analyzed using MRS medium fermented by 11 strains, respectively. And the results showed that lactic acid production was positively correlated with bacterial growth. The lactic acid yields of the strains Lactobacillus rhamnosus L9, Lactobacillus casei L10 and L11 were relatively higher, which were 15.74, 15.58, 14.74 g/L, respectively. The fermentated volatile flavor components from sorghum medium by each lactic acid bacteria were analyzed. There were 13 kinds of substances, including the important aroma components of Baijiu, such as acetic acid, caproic acid, phenylethyl acetate and phenylethyl alcohol. The relative content of acetic acid and caproic acid was relatively higher. The volatile flavor compounds produced by each bacterium were significantly different: Lactobacillus brevis L5 could produce alkanes(27.91%), Enterococcus casseliflavus L8 could produce alcohol compounds(43.14%), Lactobacillus rhamnosus L9 produced esters(7.35%), ketones(3.61%) and pyrazines(3.3%), Lactobacillus casei L11 had strong ability to produce acids(27.98%) and aromatic compounds(5.96%). Tetramethylpyrazine was produced by Lactobacillus brevis L5 only, ethanol was obviously produced by strains of L5 and L8, and 3-hydroxy-2-butanone was produced by strains of L9 and L11. All the substances above strongly influenced the flavor and taste of Baijiu. Previous studies had shown that various lactic acid bacteria in the mud had different characteristics and effects on Baijiu brewing. This study provided a basis for further tapping the functional microbes of Baijiu brewing and expanded the application of lactic acid bacteria.