The aim of this study was to identify Pseudomonas spp. in raw milk the production of extracellular enzymes (e.g., peptidases and lipases). Keywords: Pseudomonas, hydrolases, protease, lipase, glycosidase The strain 1A4R was isolated from refrigerated raw milk in Plate Count Agar (PCA; Mast . Extracellular enzyme activities produced by Pseudomonas sp. during growth on. The LipM lipase had a maximum activity at 25 °C and a broad pH optimum ranging from to In Brazil, the practice of refrigerating raw milk at the dairy farm Many of these enzymes are produced by Pseudomonas fluorescens Genetic diversity and spoilage potentials among Pseudomonas spp.

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Activities of purified LipM on different p -nitrophenyl fatty acid esters p -nitrophenyl acetate, p -nitrophenyl butyrate, p -nitrophenyl palmitate, and p -nitrophenyl phosphorylcholine were also measured according to the assay for lipolytic activity as described above. Complex regulation of AprA metalloprotease in Pseudomonas fluorescens M The purified protease Ser2 secreted by S. Enzymes from isolates of Pseudomonas fluorescens involved in food spoilage.

Although such practice on farms and in processing plants reduces the spoilage by mesophilic microorganisms, it will not prevent deterioration by psychrotrophic microorganisms 12 Affinity tags have become essential tools for the production of recombinant proteins in a wide variety of settings Waugh, The heat resistance and spoilage potential of aerobic mesophilic and thermophilic spore forming bacteria isolated from Chinese milk powders.

Growth of Pseudomonas weihenstephanensis, Pseudomonas proteolytica and Pseudomonas sp. The heat inactivation of the purified protease from Chryseobacterium indologenes did not follow first-order kinetics, but showed biphasic inactivation curves, and this protease is much more heat-labile than other psychrotrophic proteases Venter et al.

YZ did many work in experiments and helped in writing.

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As the heat treatment and refrigeration processes adopted by the dairy industry during milk processing and storage do not fully inhibit enzymatic activity nor the growth of psychrotrophic bacteria, it is important to produce milk lipae stringent good manufacturing practices to limit contamination and bacterial spoilage.


Our results are also in agreement with several other studies Koka and Weimer, ; Mu et al. The aprX-lipA operon of Pseudomonas fluorescens B To investigate the effect of metal ions on purified AprX and LipM, the reaction mixture was supplemented with 1 mM of each of the following compounds: PCR-based assay for differentiation of Pseudomonas aeruginosa from other Pseudomonas species recovered from cystic fibrosis patients.

The initial pH of the media was adjusted to 7. Although LipM exhibits the conserved serine lipase catalytic domain, it presented somewhat bypseuromonas similarity, as compared to AprX alignment, to the sequences described in the data base Figure 6. The bacterial strains and plasmids used in this study are listed in Table 1. Bacterial strains Four-hundred and eighty strains previously isolated from Chinese raw milk samples were studied Yuan et al.

Exoprotease activities of P. Genetic diversity of Gram-negative, proteolytic, psychrotrophic bacteria isolated from refrigerated raw milk.

Milk-deteriorating exoenzymes from Pseudomonas fluorescens isolated from refrigerated raw milk

Effect of heat treatment for 60 min on lipolytic activity of purified LipM. In contrast, Rajmohan et al. Proteolysis of ultra high temperature-treated casein micelles by AprX enzyme from Pseudomonas fluorescens F induces their destabilization.

The effect of lipolytic Gram-negative psychrotrophs in stored milk on the development of rancidity in Cheddar cheese. Besides, LipM showed the highest lipase activity at pH 7. In the current work, all isolates belonging to Acinetoba showed high lipolytic activity and low proteolytic activity, which is in agreement with previous studies von Neubeck et al.

Keratinolytic bacteria isolated from feather waste. Psychrotrophs and their enzymes in milk and dairy products: The residual enzyme activities can cause coagulation and degradation of milk and dairy products over time. This will be taken into consideration in the future research.

Open in a separate window. As hydrolytic enzymes from this bacterium are generally not inactivated by pasteurization or even by Ultra-High Temperature UHT treatment Griffiths et al. Biochemical tests for identification of medical bacteria.


The activity of AprX was decreased when 1 mM EDTA, an inhibitor that specifically acts on metalloproteases, was added to the reaction mixture, confirming the type of enzyme. In this work a protease and a lipase produced by P.

J Zhejiang Univ Sci B. Juan AguirreUniversidad de Chile, Chile. As lipases can cause spoilage of milk and dairy products even at low concentrations 1the production of bypseeudomonas enzymes by Pseudomonas 1A4R might negatively affect the quality of milk and dairy products.

Proteolytic activities detected on skim milk broth are of particular concern, since these enzymes could be produced during the cold storage of raw milk and contribute to the spoilage of milk after liapse treatment. In Brazil, the practice of refrigerating raw milk at the dairy farm started in the 90s, was officially instituted by the government in and it is still being implemented in some areas of the country [ Brasil, ; Brasil, ].

Amplification of aprX gene and preparation for cloning in pQEXa. Similarly, peptidase production by P. The present work aimed at the molecular characterization of a protease and a lipase produced by P. Based on the amino acid sequences, the molecular mass of both enzymes was predicted to be This approach would reduce the time for detecting these bacteria in raw milk giving flexibility for the dairy manager to choose the best use for a particular milk batch during bypseidomonas.

Increasing global demand for dairy products requires dairy manufacturers enzyms produce products with high quality and prolonged shelf-life. In this work, some isolates belonging to P. The use, distribution or reproduction in other forums is permitted, provided the original author s or sppp are credited and that the original publication in this journal is cited, in accordance with accepted academic practice.