原料乳中耐冷菌群及其产酶特点

摘要

耐冷菌及其分泌的耐热酶是原料乳中常见污染物,会导致乳制品腐败.通过16S rRNA基因测序分析了分离自上海地区原料乳的耐冷菌群,以及通过平板法研究不同耐冷菌的蛋白酶和脂肪酶活力.结果表明:所有的分离株属于9个菌纲,含33个菌属,其中数量占主要的菌属是假单胞菌(Pseudomonas)(55％)、不动杆菌(Acinetobacter)(10％)和黄杆菌(Flavobacterium)(5％),其余30个菌属占所有菌株数的30％.耐冷菌产酶能力平板法实验显示,大部分的耐冷菌都有产蛋白酶或脂肪酶的能力,不同菌属之间产酶特点存在差异.假单胞菌和黄杆菌主要表现为产蛋白酶活性,克雷伯氏菌(Klebsiella)主要表现为产脂肪酶活性,而大多数的不动杆菌没有产蛋白酶或脂肪酶活性.%Psychrotrophic bacteria and their heat-resistant enzymes are common contaminants in raw milk,leading to dairy product spoilage.The biodiversity of psychrotrophic bacteria isolated from raw milk in Shanghai was investigated by 16S rRNA sequencing and the individual isolates were evaluated for protease and lipase activities by plate culture.All isolates were classified into 33 genera in 9 classes,with Pseudomonas (55％),Acinetobacter (10％) and Flavobacterium (5％) being predominant,and the remaining 30 genera accounting for 30％ of the total number of isolates.Most isolates had the ability to produce protease or lipase,and different genera had different enzymatic profiles.Pseudomonas and Flavobacterium exhibited considerable protease activity,whereas Klebsiella showed strong lipase activity.On the other hand,most Acinetobacter isolates could produced neither protease nor lipase.