Optimation Of Condition Of Bacteriocin Production By Lactobacillus Pentosus WH12-2-1 And Characteristic Of Its Inhibitory Activity

Lactobacillus pentosus WH12-2-1 is a bacteriocin-producing strain isolated from traditional fermented dairy product of Inner Mongolia. Optimal cultural condition, medium composition and biological characteristics of producing bacteriocin were studied. In addition, preliminary isolation and purification of bacteriocin and inhibitory effect in food was also investigated.Main results and conclusions were specified as follows:(1)Optimal cultural condition and medium composition of producing bacteriocin: Study of response surfaces for maximal bacteriocin production by Lactobacillus pentosusWH12-2-1 showed the optimation was consist of 10 g/L soy peptone, 5 g/L beef extract, 5 g/L yeast powder , 30 g/L glucose, 6 g/L sodium citrate, 6 g/L K2HPO4, 15 g/L CH3COONa, 2 g/L Tween 80, 1 g/L MgSO4, 50 mg/L MnSO4 and 50 mg/L FeSO4. And start pH was 7.0, inoculum was 1% and static cultured for 48h at 37℃. With these conditions, crude extract solution of bacteriocin arbitary units could achieve as much as 493.90IU/mL.(2)Biological characteristics of crude extract solution of bacteriocin: This crude extract solution showed its antibacterial activity between pH3.0 and 6.0 and the highest activity is associated with pH values in the range of 3.0 to 5.0. No activity was detected under neutral and alkalinous conditions. Bacteriocin showed stable activity after different thermal and frozen treatments. Activity of culture filtrates was displayed against both Gram-positive and Gram-negative bacteria with a broad spectrum . No activity was detected to yeasts.(3)Purification of bacteriocin: crude extract of bacteriocin showed the higher inhibitory activity after ultrafiltration. And then through gel filtration chromatography by Sephadex G-25, two eluted peaks were collected and checked for bacteriocin activity. The second peak of collective solution was of only inhibitory activity. The molecular mass of the purified bacteriocin was between 3kDa and 5kDa which indicated it is a micromolecule peptides.(4)Inhibitory effect in food: No inhibitory effect was observed in raw milk by purified bacteriocin of L . pentosus WH12-2-1.But in 30% tomato juice, strong inhibitory effect was observed to both Bacillus cereus and Escherichia coli O157:H7.In addition, inhibitory effect to Bacillus cereus was higher than Escherichia coli in tomato juice. Besides, inhibitory activity to Escherichia coli O157:H7 in yoghurt drink was higher than in 30% tomato juice.