Isolation,Identification And Characterization Of Lactic Acid Bacteria From Traditional Fermented Vegetables

The traditional fermented vegetables in China have a long history and the northeast and southwest are the main areas.Lactic acid bacteria(LAB)are the dominant microorganisms in fermented vegetables.They can not only improve the flavor and nutritional value of the products during the fermentation process,but also prolong the storage period by producing antibacterial substances such as organic acids.It is known that the fermentation characteristics and functional properties of LAB are very important,However,little or no information has been reported on it statistically.In this study,80 samples of fermented vegetables(fermented cabbage)were collected from the northeast(Heilongjiang,Jilin,Liaoning and Inner Mongolia)and 64 samples of fermented vegetables(fermented mustard)were collected from the southwest(Sichuan and Chongqing).And 351 strains were isolated from these samples.For these strains,the ability of nitrite degradation,producting gamma-aminobutyric acid(GABA),phenyllacticacid(PLA)and 4-hydroxyphenyl lactic acid(4-OH-PLA),cholesterol-lowering and antioxidationwere studied.It is intended to reveal the distribution of LAB species that can be separatedfrom Chinese traditional fermented vegetables,as well as the relationship between fermentation characteristics and functional properties to geographical and microbial species.The main conclusions are as follows.The 351 strains that isolated from the traditional fermented vegetables belong to four generas and 36 species.The species of LABfrom the Southwest are obviously different fromthe Northeastern ones.The Lactococcus fromthe southwest are Pediococcus,which can resistant to Ethanol,while in the northeast,in addition to Pediococcus,Enterococcus and Pseudomonas aeruginosaalso exist;And among the LABs detected in all samples,Lactobacillus plantarum and Lactobacillus brevis are predominant species.Although the nitrite degradation ability of LAB has a certain specificityamong different strains,the ability of these strains that isolated from fermented vegetables in northeast are significantly higher than that in southwest(P<0.001);and the ability of Lactobacillus arealso significantly higher than Lactococcus.There are also significant difference between different strains(P<0.05).Only 3% of the strains have the ability to produce GABA,and these strainsare concentrated in Lactobacillus buchneri(5 strains),Lactobacillus brevis(4 strains)and Lactobacillus plantarum(1 strain).In general,Lactobacillus brevis has a strong ability to produce GABA.And it was found that about 67.0%-92.1% of glutamate,as a substrate,can be converted into GABA within 48 h.Most LABalso have the ability to PLA and OH-PLA,and the ability to produce PLA and OH-4-PLAis significantly positive correlation(P<0.05,R=0.883);The ability of Lactobacillus to produce PLA and OH-4-PLAis also significantly higher than that of Lactococcus(P < 0.001).In general,Lactobacillus crustorum has the highest yield of PLA and OH-4-PLA and the yield increased significantly when the substrates were added,such as L-pyruvate,phenylalanine,tyrosine and 4-hydroxy pyruvic acid.Based on the bile salt deconjugation ability,the cholesterol reducing potential of LAB was analyzed.The detection rate of bile salt hydrolasepositive strains from these LAB that isolated from fermented vegetables in Northeast and the bile salt deconjugation abilityof these LAB were significantly higher than that in Southwest(P<0.05);About 50% of the strains have bile salt hydrolase activity,and for these strains,the deconjugation ability of glycineconjugating bile salt of were significantly(P<0.05)higher than taurine conjugating bile salt.Reducting metal ion ability and scavenging DPPH radical ability of these LAB,which isolated from fermented vegetables in northeast is significantly higher than that in southwest(P<0.05),but there is no significant difference in the inhibition of linoleic acid peroxidation(P>0.05).And the ability of Lactococcus to inhibit linoleic acid peroxidation is significantly higher than that of Lactobacillus(P<0.05).