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首页> 外文期刊>Journal of Microbiology, Biotechnology and Food Sciences >GENETIC DIVESITY AND EXTRACELULLAR ENZYMATIC ACTIVITY OF BACILLUS LICHENIFORMIS STRAINS FROM MILK POWDER
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GENETIC DIVESITY AND EXTRACELULLAR ENZYMATIC ACTIVITY OF BACILLUS LICHENIFORMIS STRAINS FROM MILK POWDER

机译：牛奶粉中芽孢杆菌的遗传多样性和细胞外酶活性

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A total of 379 B. licheniformis strains isolated from commercial milk powder were characterized genotypically and phenotypically. RAPD analysis yielded three different profiles, which include all isolates in this study, which could be assigned to strain F (n=375) or strain G (n=4), strain F also could be divided into two groups (group 1, n = 117; group 2, n = 258). Clustering by pairwise sequence similarity and phylogenetic relationships between isolates based on comparisons of the 16S rRNA gene sequence, showed two well defined groups. Group I contains all isolates tested belonging to genotype F, and Group II consists of three G genotype isolates. A total of 32 isolates, respecting the representation of each genotype, were randomly selected for extracellular enzymatic activity plate assays. Most isolates (25 out of 32) showed extracellular proteinase, lipase and amylase activity. Hydrolytic activities tested in this study are strain-dependent and none enzymatic activity could be linked to a defined group at genetic level. Preliminar characterization of proteolytic crude enzyme extract suggests the presence of a metal-activated serine protease active at an optimun temperature of 60 oC. The exoenzymes production and its variation against different factors such as temperature, is isolate dependent so these results indicate that not all B. licheniformis strains may mean the same risk to process or product quality.
机译：从市售奶粉中分离出的总共379种地衣芽孢杆菌菌株在基因型和表型上得到了表征。 RAPD分析得出三种不同的图谱，包括本研究中的所有分离株，它们可以分为菌株F（n = 375）或菌株G（n = 4），菌株F也可以分为两组（第1组，n = 117;第2组，n = 258）。根据16S rRNA基因序列的比较，通过分离物之间的成对序列相似性和系统发育关系进行聚类，显示了两个定义明确的组。组I包含所有测试的属于基因型F的分离株，组II由三个G基因型分离株组成。随机选择每种基因型代表的总共32个分离株用于细胞外酶活性板测定。大多数分离株（32个中的25个）显示出胞外蛋白酶，脂肪酶和淀粉酶活性。在这项研究中测试的水解活性是菌株依赖性的，没有任何酶活性可以在遗传水平上与确定的组相关。蛋白水解粗酶提取物的初步表征表明存在金属活化的丝氨酸蛋白酶，该蛋白在最适温度为60 oC时具有活性。外切酶的产生及其对不同因素（例如温度）的变化是独立的，因此这些结果表明，并非所有地衣芽孢杆菌菌株都可能对加工或产品质量产生相同的风险。

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