L. Paracasei (lactobacillus Paracasei) Hd1.7 Producing Peptide Optimization And Peptide Separation

Antibacterial peptides (ABP), produced by lactic acid bacteria, show their advantages in safety and lowcost. ABP is now paid more and more attention to. The ABP produced by Lactobacillus. paracesei HD 1.7 can inhibit not only gram positive bacterium, but also gram negative bacterium and yeast. It can keep steady when boiled in high temperature. Research was done on the components of medium to optimize the production of the ABP, the purification of the ABP was studied, and the biological features of the ABP were detected. This research laid foundations for the production of the ABP and much more attentions would be paid on the research of the sites controling indicators and the gene expression of the ABP.Based on the compariation of the components of mediumof L. paracasei HD1.7, an optimal medium was obtained: peptone 30g/L, glucose 10g/L, K₂HPO₄1.5g/L, NaHPO₄ 0.2g/L, NaSO₃ 7g/L, MgSO₄ 0.1 g/L, MnSO₄ 0.025g/L, tween-80 1.0mL/L, with initial pH5.5.When studied on the separation and purification of the ABP, the fermentation liquid was isolated by the CM Sepharose Fast Flow Cation-eachange chromatography and Sephadex G-25, G-10 gel filtration chromatography. The active components (G10a, G10b, G10c, G10d and G10e) were obtained; the highest activity was showed by G10d. Its molecular weight was estimated to be under 10kDa, according to SDS-PAGE.The biological features of the ABP showed that the optimum pH was 4.0. The bacteriocin was steady in acid conditions. It was still active after boiled in 121℃for 15mins, which showed good thermal stability. The inhibition spectrum of the ABP was very wide, it could inhibit both positive bacteria and negative bacteria, and also effected on yeast. It was sensitive to typsin, but insensitive to pepsin, papain and K protease. The ABP inhibited Bacillus subtilis from growing rather than killing it. The ABP still kept high activity when preservated in 4℃for 4 months.