【作者】 李莉；

【导师】 孟和毕力格；

【作者基本信息】 内蒙古农业大学 ， 食品科学， 2009， 硕士

【摘要】 本试验以分离自内蒙古传统乳制品中的戊糖乳杆菌(Lactobacillus pentosus)WH12-2-1为研究对象,对其产细菌素的培养条件、培养基成分和生物学特性进行了分析,并对该细菌素进行了初步的分离纯化和在不同食品中抑菌作用的研究。主要研究结论如下:(1)L . pentosus WH12-2-1产细菌素最佳培养条件和培养基成分的优化:采用响应面法确定了L . pentosus WH12-2-1产细菌素最佳培养基成分和培养条件为大豆蛋白胨10 g/L,牛肉膏5 g/L,酵母粉5 g/L,葡萄糖30 g/L,柠檬酸钠6 g/L,磷酸氢二钾6 g/L,乙酸钠15 g/L,Tween 80 2 g/L,硫酸镁1 g/L,硫酸锰50 mg/L,硫酸亚铁50 mg/L,起始pH值7.0,1%的接种量,37℃静置培养48h。此条件下该细菌素粗提液的效价值为493.90 IU/mL。(2)细菌素粗提液的生物学特性:L . pentosus WH12-2-1的细菌素粗提液在pH 3.0～6.0范围内具有抑菌活性,其中在pH 3.0～5.0范围内活性最强,而在中性及碱性条件下则失去活性。该粗提液经过不同温度、时间的加热和冷冻冷藏处理后,其抑菌活性均显示出了较强的稳定性。抑菌谱较广,不仅对革兰氏阳性菌有抑菌作用,而且对革兰氏阴性菌也有抑菌作用,但是对酵母菌无抑菌作用。(3)细菌素的纯化:L . pentosus WH12-2-1的细菌素粗提液经过超滤后,分子量为3kDa<M<5kDa的组分抑菌活性最强。该组分经过Sephadex G-25凝胶过滤层析,出现两个洗脱峰,对这两个洗脱峰的收集液进行测定,只有第二个峰的收集液有抑菌活性,说明该细菌素的主要抑菌活性物质的分子量在3kDa<M<5kDa范围内,是一种小分子肽类物质。(4)细菌素在不同食品中的抑菌作用:纯化后的L . pentosus WH12-2-1的细菌素在鲜奶中无抑菌作用,在30%番茄汁中对蜡样芽胞杆菌和大肠杆菌O157:H7都有较强的抑菌作用,且对蜡样芽胞杆菌的抑菌作用强于对大肠杆菌O157:H7的抑菌作用。在调配型酸乳饮料中对大肠杆菌O157:H7的抑菌作用强于30%番茄汁中对大肠杆菌O157:H7的抑菌作用。更多还原

【Abstract】 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.更多还原