| Object：Lactic acid bacteria is a class of microorganisms has been widely used in the food industry, thedevelopment and utilization of lactic acid bacteria is research hotspot of today’s domestic and foreignresearch scholars, to understand the lactic acid bacteria biodiversity is premise to develop it, psychrotrophslactic acid bacteria is not common at home and abroad, the psychrotrophs lactic acid bacteria due to itsstronger growth rate in a refrigerated environment so that it has a broad application prospects in the field offood and biological engineering. Bacteriocin generally have a good effect in the food preservation,compared with chemical preservatives, Bacteriocin’s advantages of non-toxic, non-resistant, no residue, noside effects to extend the warranty of the food has become the hot object of the biological preservatives,producing bacteriocin strains isolated and purified from the psychrotrophs lactic acid bacteria is theprimary and based problem. Therefore, study on Xinjiang unique cold-water fish resources psychrotrophslactic acid bacteria biodiversity and screening of strains producing bacteriocins is significantly.Methods：This study based on the Irtysh River Basin unique wild cold-water fish resources, isolated andpurified psychrotrophs lactic acid bacteria by a traditional pure culture method form fish gut andsequencing to study the diversity of their systems, while using three primers REP-PCR molecular geneticstechnical study its biodiversity. Screening produced bacteriocins’s strains of lactic acid bacteria from thepure culture, study on the produced bacteriocins of strain prime biology characteristics for the applicationof psychrotrophs lactic acid bacteria and the bacteriocins.Results：Isolated the89psychrophile strains by dilution plate method, in which is65.2%Gram-positivebacteria and34.8%negative bacteria. Based on colonies, color and cell morphology, Gram staining andliquid cultured features preliminary think the45suspected LAB Strains. The strains’s phylogenetic treeanalysis: psychrotrophs lactic acid bacteria isolated from the cold-water fish samples collected43belonging to six genera: Enterococcus, Carnobacterium, Brochothrix, Weissella, Streptococcus,Lactococcus. Enterococcus and Lactococcus is dominant flora. Enterococcus occupied most the totalproportion of bacteria in the dominant species and contributed most for the cold-water fish gut culturablepsychrotrophs lactic acid bacteria diversity. This study shows that cold-water fish gut has a rich diversity ofculture psychrotrophs LAB. The cold-water fish intestinal isolated culture LAB highest growth temperaturenot higher than37℃, the optimum growth temperature is15-30°C, growth and reproduction at4℃,most of which are psychrotrophs.Isolated and purified43psychrotrophs lactic acid bacteria in the above chapter as target bacteria,selected three Gram-positive bacteria Staphylococcus aureus, Bacillus subtilis, Listeria and aGram-negative bacteria E. coli as indicator bacteria. After exclusion of acid, over interference of thehydrogen peroxide and protein nature determination shows the11bacteria will inhibit the growth ofspoilage bacteria in varying degrees, the screening lactic acid bacteria of antibacterial properties haveLactococcus, Enterococcus and Weiss genus.Enterococci MB2-1and Lactococcus MD-1selected from psychrotrophs lactic acid bacteria fordetailed study which have higher production of bacteriocins and antibacterial activity widely in thelow-temperature, and growth rate faster in the low-temperature environment. Having a higher heatresistance, and the antibacterial activity stability in the acidic, neutral and slightly alkaline environment,with a chelating agent SDS having a synergistic phenomenon, the most important is the sensitivity toprotease, applied as a preservative in food does not cause bad side effects. Therefore, this study makessense as a food preservative of psychrotrophs lactic acid bacteria, laid the basis for the industrialapplication of biotechnology in food preservative. |
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