Isolation and Identification of Lactic Acid Bacteria from Mud of Baijiu and Comparison of Fermented Volatile Flavor Compounds(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)
摘要
strains of lactic acid bacteria were isolated from mud of Baijiu and identified by 16S 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 L<sub>9</sub>, Lactobacillus casei L<sub>10</sub> and L<sub>11</sub> were relatively higher, which were 15.74,5.58,4.74g/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 L<sub>5</sub> could produce alkanes(27.91%), Enterococcus casseliflavus L<sub>8</sub> could produce alcohol compounds(43.14%), Lactobacillus rhamnosus L<sub>9</sub> produced esters(7.35%), ketones(3.61%) and pyrazines(3.3%), Lactobacillus casei L<sub>11</sub> had strong ability to produce acids(27.98%) and aromatic compounds(5.96%). Tetramethylpyrazine was produced by Lactobacillus brevis L<sub>5</sub> only, ethanol was obviously produced by strains of L<sub>5</sub> and L<sub>8</sub>, and 3-hydroxy-2-butanone was produced by strains of L<sub>9</sub> and L<sub>11</sub>. 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 Baiji