| 摘要: |
| 【目的】对冷藏原料乳中易污染的嗜冷菌进行分离筛选，为提高乳品品质、控制乳品质量提供参考。【方法】从冷藏原料乳中筛选出1株嗜冷菌，通过形态学观察、生理生化试验、16S rDNA分子生物学分析，对该株嗜冷菌进行鉴定；并采用福林 酚试剂法、蛋白酶定性检测试验、耐热性试验以及牛奶酸度、黏度影响等试验，对其产酶特性进行研究。【结果】从冷藏原料乳中分离出的该株嗜冷菌为革兰氏阴性短杆菌，与GenBank中登录的荧光假单胞菌的生理生化特征相符，二者同源性为92.5%～97.6%。对该菌产胞外酶能力的研究发现，该菌所产胞外酶为一种耐热碱性蛋白酶，最适温度为30 ℃，最适pH为8.0，可引起牛乳黏度增大、凝集和乳清析出。【结论】从冷藏原料乳中分离出了嗜冷荧光假单胞菌，该菌所产胞外碱性蛋白酶会引起牛乳黏度增加、凝集和乳清析出，明显缩短乳品的保质期。 |
| 关键词: 牛乳 冷藏原料乳 荧光假单胞菌 碱性蛋白酶 热稳定性 牛乳酸度 牛乳黏度 |
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| 基金项目:安徽省自然科学基金项目(11040606M91)；安徽省试验区和试点创新基金项目（12z0102055） |
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| Isolation and identification of Pseudomonas fluorescens from refrigerated raw milk and characterization of its protease |
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| Abstract: |
| 【Objective】Pseudomonas fluorescens was isolated and identified from refrigerated raw milk to improve and control dairy quality.【Method】A strain of psychrophile was identified as P.fluorescens based on cell morphological properties,physic-biochemical characteristics and homologous analysis in 16S rDNA sequence.The characterization of the protease produced by the pseudomonas was investigated using Folin-Phenol reagent method,protease qualitative tests,heat assay,and examination of its influence on the viscosity and acidity of milk. 【Result】The isolated strain was Gram negative short bacillus.It had the same physiological and biochemical characteristics with P.fluorescens in Genbank with a homology of 92.5%-97.6%.The extracellular protease (ECPase) identified was a high temperature resistant alkali protease with optimum reaction temperature of 30 ℃ and optimum reaction pH of 8.0.The extracellular protease can cause the increase of milk viscosity and milk agglutination.【Conclusion】A strain of psychrophilic P.fluorescens was isolated from refrigerated raw milk.The produced extracellular protease (ECPase) could cause the increase of viscosity agglutination,and shorten the shelf life of milk. |
| Key words: cow milk refrigerated raw milk Pseudomonas fluorescens alkaline protease thermal stability viscosity of milk acidity of milk |
