Bacteriocin-producing Lactic Acid Bacteria Isolated From Traditional Cheeses In Xinjiang As Potential Bio-control Agents In Food:Isolation, Screening And Phylogeny

Aim:Lactic acid bacteria were widely used in the food processing as microbe,they have a very important position in the food industry. Studies have shown that lactic acid bacteria as a natural preservative used in the food storage can improve the safety of food. Lactic acid bacteria can inhibit the growth of pathogens as probiotics. They not only made a contribution to the storage of raw materials,guarantee the nutritional quality,extension of shelf life,but also inhibiting microorganism to keep the food quality. Bacteriocin known as the “biological food preservative”, it is non-toxic,no resistance,no side effect,no residue which can replace chemic preservatives and antibiotics in food production,bacteriocin has great application value in the food preservation field. Therefore,screening and purification of high quality producing-bacteriocin lactic acid bacteria as biological preservatives,it has a highly research value. Method:This sample was collected from cheese made by herders in YiLi, ZhaoSu, GongLiu, XinYuan,KeKeTuoHai of XinJiang region. By dependent-culture method,lactic acid bacteria were isolated using five media including MRS,Lactobacillus selective medium,M17,Bile esculin sodium azide medium,Elliker and sequencing the diversity of phylogeny. Using agar diffusion method of Oxford cup to screen the producing- bacteriocin lactic acid bacteria,studying the biological characterization of bacteriocin,studying on lactic acid bacteria and bacteriocin as preservative for some theoretical and practical basis. Conclusion:1. Isolated the 285 strains by selective media. By preliminary screening, 202 presumptive lactic acid bacteria were gram positive and catalase negative,based on the sequence analysis of 16 SrRNA,163 srains were belonged to lactic acid bacteria which included 5 genus:Enterococcus,Lactobacillus,Lactococcus,Weissella and Streptococcus was predominant strain in which 62% of total propotion. 2. 75 strains had a different degree to inhibit the Listeria monocytogenes,Bacillus subtilis, E. coli and Staphylococcus aureus. Excluding the effect of organic acid and hydrogen peroxide,the result shows 12 srains still had a clear impact on inhibiting the listeria monocytogenes. after enzyme treatment,the 12 bacteriostatic activity of supernatant feel sharply even disappeared,the fermented supernatant may exist the bacteriocin or other antimicrobial peptide composition,12 strains could be producing –bacteriocin lactic acid bacteria. 3. Selected the strain Enterococcus sp. KKTHD-13 and Lactococcus sp.ZS5-11,which had significant antimicrobial activity to four indicator strains. According to the further explore the biological characteristics of its,the study has shown that two supernatant still had activity at 60℃-100℃. They had a better thermal stability;supernatant had a relative wide antibacterial ph range(2-9);By different enzyme treatment,two strains lost the antibacterial activity,they had the high security,it is the trend that replaced the chemical food additives used in the food preservation as the biological preservative.