Screening Of Lactobacillus Being Of Antibacterial Activity And Studying On Characteristics Of Antibacterial Compounds

The strains being of antibacterial activity were screened from 13 lactobacillus isolated from traditional grain fermentation food Acid-Gruel in Inner Mongolia. Their antibacterial ability and characteristics of antimicrobial compounds were studied too. The results were showed as follows:(1) The inhibition abilities of 13 strains on typhoid salmonella, escherichia coli, bacillus subtilis and staphylococcus aureus are different. The antibacterial effect of these strains on typhoid salmonella is the most obvious, and that on staphylococcus aureus is a bit poor. Among these, for typhoid salmonella, antibacterial activity of SZL-1 and SZL-7 is the strongest; for E.coli, that of SZL-2 and SZL-5 is the strongest; for bacillus subtilis, that of SZL-8 and SZL-11 is strongest, and that of SZL-3 and SZL-8 on staphylococcus aureus is the strongest.(2) Antibacterial activity of fermentation medium and metabolite of 13 strains can be detected.The fermentation medium and metabolites showed good thermal stability, and the antibacterial activity basically same;As pH value increased, the antibacterial activity gradually reduced following pH value increased. In addition, SZL-1 and SZL-12 have inhibition activity even in pH6.0, and the others basically have no antibacterial activity in weak acidic, neutral or alkaline conditions. Metabolites were treateded by catalase,the antibacterial activity of SZL-1 and SZL-12 is decreased obviously,the others basically have no change;Then,metabolites of SZL-1 and SZL-12 were treateded by proteinase K, pepsin, trypsin,papain,and lysozyme,the antimicrobial activity were significantly reduced. It indicated that antibacterial substances were protease-sensitive.Therefore, there were protein bacteriocins in the antibacterial material.and antibacterial activity were not changed while treated at 100℃for 30min. The main inhibition material substance of 13 lactobacillus were acidic substance (mainly lactic acid) and bacteriocins.(3)By single factor experiments and orthogonal experiments,the fermentation condition for SZL-1 and SZL-12 on production of Bacteriocin was optimize.The result showed that the optimum inoculation quantity of SZL-1 is 7%, initial pH was 6.0,culturing temperature at 37℃for 24 hours. The result showed that the optimum inoculation quantity of SZL-12 is 5%, initial pH was 6.0,culturing temperature at 37℃for 36 hours.(4) The biological features of bacteriocin were studied. the bacteriocin produced by SZL-1 showed good thermal stability, and pH ranged is 2.0⁸.0. Na⁺, K⁺ and Fe²⁺ can promote the antibacterial activity, whereas Ca²⁺ and Zn²⁺ inhibited it. The Bacteriocin produced by SZL-12 also showed good thermal stability,and pH ranged is 2.0⁷.0, Na⁺,Zn²⁺ and Fe²⁺ can promote the antibacteria activity,whereas K⁺ and Ca²⁺ inhibited it.Moreover bacteriocin produced by SZL-1 and SZL-12 had obvious inhibit activity on antibacterial upon Gram-positive bacteria and Gram-negative bacteria, but no action on yeast. And antibacterial spectrum was wide.