【作者】 徐洪涛；

【导师】 范圣第； 权春善；

【作者基本信息】 大连理工大学 ， 生物化工， 2006， 硕士

【摘要】 从辣白菜、酸奶等12种发酵食品中分离出420株乳酸菌,通过琼脂点扩散交叉拮抗试验从中筛选出一株对沙门氏菌有明显抗性的乳酸菌,该菌株菌落较小、圆形、淡乳白色、边缘整齐光滑,单生、成对生或短链状,兼性厌氧;革兰氏染色呈阳性、无芽孢。经API生理生化反应、16SrDNA同源性分析鉴定该菌株为类植物乳杆菌X-600。 通过硫酸铵沉淀或正丁醇提取、阳离子交换层析、凝胶过滤、反相高效液相色谱等分离纯化过程,从类植物乳杆菌的发酵液中分离纯化出一种活性物质LPX-600。比较硫酸铵沉淀和正丁醇提取两种粗提方法发现,相比于硫酸铵沉淀,正丁醇提取活性物质的效果更好,两种分离方法最终的活力回收率分别为1.02%和0.54%。纯化的活性物质经高效液相鉴定其纯度达到95%以上,经透析和凝胶过滤层析判断其分子量大约在600～1,000Da。 LPX-600在酸性条件下活性较高,对热稳定(121℃,15min部分失活),在蛋白酶K、胃蛋白酶、木瓜蛋白酶作用下不失活,Tricine SDS-PAGE检测发现凝胶上没有清晰的条带,因此判断该活性物质不是蛋白或多肽,LPX-600抑菌谱较宽,对沙门氏菌、变形杆菌、金黄色葡萄球菌、粘性沙雷氏菌、肺炎克雷伯氏菌等多种革兰氏阳性和阴性致病菌有很强的抑菌活性,与乳酸链球菌素、乳酸、柠檬酸相比,LPX-600对沙门氏菌具有更明显的抑菌效果。 将类植物乳杆菌发酵液喷洒于接种沙门氏菌的新鲜猪肉上,分别在常温和低温贮藏,在贮藏期间,抽样考察发酵液对新鲜猪肉的抑菌效果,并对猪肉的pH、水分含量、感官质量等指标进行评价。结果表明:发酵液在常温和低温时均能够显著抑制沙门氏菌的生长;与对照组相比,经发酵液处理的猪肉表面显微酸性,猪肉的水分含量随贮藏时间的延长略有降低,发酵液对新鲜猪肉的感官质量无不良影响,经发酵液处理的猪肉的感官质量要明显好于未经处理的猪肉。综合考察不同浓度的类植物乳杆菌发酵液的作用效果,发现2倍稀释的类植物乳杆菌发酵液为最适浓度,能够有效抑制沙门氏菌的生长,延长猪肉的货架期,而且可以改善猪肉的风味和感官质量,降低猪肉的水分含量。更多还原

【Abstract】 In this study, 420 LAB (Latic acid bacteria) strains were isolated from twelve kinds of fermented foods. Among them, one LAB strain exhibited strong inhibition to the growth of Salmonella sp., and it was identified as Lactobacillus paraplantarum X-600 according to the characteristics of morphology, physiology and biochemistry tests (API 50 CHB/E system) and the comparison of 16S rDNA sequence. The strain produces a low-molecular-weight antimicrobial substance designated LPX-600, which is bactericidal for many Gram positive and negative pathogen and spoilage bacteria, including Salmonella sp., Escherichia coli, Staphylococcus aureus, Serratia marcescens, Klebsiella pneumoniae, etc.LPX-600 was purified through ammonium sulfate precipitation or n-butyl alcohol extraction, cation-exchange chromatography, gel filtration and reverse-phase HPLC. Molecular weight of LPX-600 ranged from 600 Da to 1,000 Da by the analysis of dialysis and gel filtration and the purity reached 95% by HPLC analysi. The antimicrobial substance was heat-stable and only partly inactivated after treatment at 121℃ for 15min.The LPX-600 was also stable to proteolytic enzymes treatment (protease K, pepsin, papain).Lactobacillus paraplantarum X-600 have potential application in foods. Experiments were conducted to study the activity of fermented solution against Salmonella sp on fresh poak and the influence of fermented solution on surface pH, water content and sensory quality of poak meat. The results indicated that fermented solution can effectively inhibit the growth of Salmonella sp. on poak meat at 4℃ and room temperature. Surface pH of fresh poak decreased after the treatment of fermented solution. Water content of poak meat gradually decreased during storage. Sensory evaluation showed that the addition of fermented solution had no negative effect on sensory quality of fresh poak.更多还原