Andreani Nadia Andrea, Carraro Lisa, Fasolato Luca, Balzan Stefania, Lucchini Rosaria, Novelli Enrico, Cardazzo Barbara
Department of Comparative Biomedicine and Food Science, University of Padua , Legnaro (PD), Italy.
Institute for Experimental Veterinary Medicine of Venezie , Legnaro (PD), Italy.
Ital J Food Saf. 2016 Dec 6;5(4):6175. doi: 10.4081/ijfs.2016.6175. eCollection 2016 Sep 20.
Bacterial proteases are involved in food spoilage and shelf-life reduction. Among the bacterial proteases, a predominant role in spoilage of dairy products seems to be played by the thermostable metallo-protease AprX, which is produced by various strains of . Differences in AprX enzyme activity among different strains were highlighted, but the most proteolytic strains were not identified. In this study, the presence of the gene was evaluated in 69 strains isolated from food matrices and 18 reference strains belonging to the group, which had been previously typed by the multi locus sequence typing method. Subsequently, a subset of reference strains was inoculated in ultra-high temperature milk, and the expression of the gene was evaluated at 22 and 6°C. On the same milk samples, the proteolytic activity was then evaluated through Azocasein and trinitrobenzenesulfonic acid solution assays. Finally, to assess the applicability of the former assay directly on dairy products the proteolityc activity was tested on industrial samples using the Azocasein assay. These results demonstrate the spread of gene in most strains tested and the applicability of Azocasein assay to monitor the proteolytic activity in dairy products.
细菌蛋白酶与食品变质和保质期缩短有关。在细菌蛋白酶中，热稳定金属蛋白酶AprX似乎在乳制品变质中起主要作用，AprX由多种菌株产生。不同菌株之间AprX酶活性的差异得到了突出显示，但未鉴定出蛋白水解活性最强的菌株。在本研究中，对从食品基质中分离出的69株菌株以及属于该组的18株参考菌株进行了基因存在情况的评估，这些菌株先前已通过多位点序列分型方法进行了分型。随后，将一部分参考菌株接种到超高温灭菌牛奶中，并在22℃和6℃下评估基因的表达。然后，通过偶氮酪蛋白和三硝基苯磺酸溶液测定法对相同的牛奶样品进行蛋白水解活性评估。最后，为了评估前一种测定法直接应用于乳制品的适用性，使用偶氮酪蛋白测定法对工业样品的蛋白水解活性进行了测试。这些结果证明了基因在大多数测试菌株中的传播以及偶氮酪蛋白测定法在监测乳制品中蛋白水解活性方面的适用性。
