Characterisation of the thermostable protease AprX in strains of Pseudomonas fluorescens and impact on the shelf-life of dairy products: preliminary results

Andreani, Nadia and Carraro, Lisa and Fasolato, Luca and Balzan, Stefania and Lucchini, Rosaria and Novelli, Enrico and Cardazzo, Barbara (2016) Characterisation of the thermostable protease AprX in strains of Pseudomonas fluorescens and impact on the shelf-life of dairy products: preliminary results. Italian Journal of Food Safety, 5 (4). ISSN 2239-7132

Full content URL: http://dx.doi.org/10.4081/ijfs.2016.6175

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Abstract

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 Pseudomonas fluorescens. 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 aprX gene was evaluated in 69 strains isolated from food matrices and 18 reference strains belonging to the P. fluorescens 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 aprX 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 ricotta samples using the Azocasein assay. These results demonstrate the spread of aprX gene in most strains tested and the applicability of Azocasein assay to monitor the proteolytic activity in dairy products.

Keywords:Pseudomonas fluorescens, Spoilage, Dairy products, AprX., JCOpen
Subjects:D Veterinary Sciences, Agriculture and related subjects > D620 Food Hygiene
C Biological Sciences > C510 Applied Microbiology
Divisions:College of Science > School of Life Sciences
ID Code:27505
Deposited On:19 May 2017 09:27

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