Screen Of Leuconostoc From Soil And Study On Bacteriocins Produced By Leuconostoc

Leuconostoc spp. is a genus of Gram-positive, facultatively anaerobic, heteromorphosis lactic acid bacteria(LAB). Although their population is often small compared with that of aerobic bacteria and yeasts, Leuconostoc strains present in many environments originate from green vegetation and roots which constitute their natural ecological niche. From this natural habitat, they can easily be screened from various niches including plant materials such as vegetables or their fermentation products, milk or usually in dairy products, and fermented meat sources. There is no reports of Leuconostoc spp. screened from soil.In this study, Leuconostoc from soil of Xining in Qinghai Province, and Golden Lotus mountain in Guyuan County, Hebei Province, were screened. After series of physiological and biochemical tests, a Gram-positive, catalase-negative, non-sporulating, facultatively anaerobic, spherical shaped in pair or short chain bacteria was isolated respectively from the two soil. The taxonomic status of the two strains were definited by these results. Xining strain was classified as the genus of Leuconostoc mesenteroides subsp. mesenteroides, and Guyuan strain was classified as Leuconostoc. pseudomesenteroides also by the phylogenetic tree based on the 16S rDNA sequences. It was named kimshi005 and the Accession Number of this 16S rDNA sequences was GU130195 in GenBank.Leuconostoc can produce many series of fuctional substances, and bacteriocin is one of them. In this study, Leuconostoc mesenteroides CGMCC1.10327 was used to produce bacteriocins, which are active against Escherichia coli DH 5α, Staphylococcus aureus ATCC 6538P and Micrococcus luteus ATCC 10240A. The influences of medium composition, pH, and inoculum on bacteriocin production were investigated by using E. coli as the indicator strain. Finally, 3.0 g yeast extract powder, 3.0 g ammonium citrate, 0.039 g manganous sulphate tetrahydrate, 5.0 g sodium acetate, 2.0 g K2HPO4, and 1.6 ml Tween-80 were fixed with 10.0 g glucose in one liter medium. Inoculum 1% and original pH of 6.2 were used during the culture. After the native polyacrylamide gel electrophoresis, Rf value was defined and four bacteriocin bands with Rf value of 0.272, 0.502, 0.630, and 0.917 were active against E. coli, while others did not have the anti-DH5αactivity. It means that four bacteriocins with different molecular weight were produced by this strain.The significances of this study was that Leuconostoc spp. were screened form general soil, and were identified by physiological and biochemical tests and the phylogenetic tree based on the 16S rDNA sequences. The method we used in this study will help to screen and identify strains from soil or other sources which have low amount of Leuconostoc. Meanwhile, as Leuconostoc mesenteroides CGMCC1.10327 was a new strain isolated from Kimchi produced in Tianjin, study on its bacteriocins will help to a further application of this strain.