原料乳中产耐热蛋白酶细菌的鉴定及其酶学特性研究

Identification of a Bacterium Isolated from Raw Milk and Study on Its Heat-Stable Protease

为了研究UHT乳在货架期内发生水解、凝块、变苦等品质劣变现象的原因,从原料乳中分离得到一株产耐热蛋白酶细菌,通过细菌形态观察、生理生化试验、脂肪酸分析、16S rDNA基因序列测定及16-23S rRNA间区序列分析,对该菌株进行鉴定,并对其所产蛋白酶进行初步研究。结果表明:该菌株属于荧光假单孢杆菌。该菌株所产的耐热蛋白酶的最适温度为40℃,最适pH为6.8。该蛋白酶可以耐受140℃,4 s热处理。

UHT milk can be clotted or hydrolyzed by the heat-stable protease from Psychrotrophs bacteria in raw milk,resulting in bitter taste and other quality deterioration in shelf life. One of bacterium from raw milk was identified based on morphology,physiology,biochemistry analysis, 16S rDNA and 16-23S rRNA sequence analysis. The bacterium （named Rml2） was identified as Pseudomonads fluorescens. The optimal catalytic temperature and pH of the protease from Rml2 were 40 ℃ and 6.8 respectively. After heat treatment （140 ℃ ,4 s）,the rest of activity of protease was only 6.66% that of the original preparation.