Milk-deteriorating exoenzymes from Pseudomonas fluorescens 041 isolated from refrigerated raw milk

• Published in: Brazilian journal of microbiology Vol. 46; no. 1; pp. 207 - 217
• Main Authors: Martins, Maurilio L, Pinto, Uelinton M, Riedel, Katharina, Vanetti, Maria C D
• Format: Journal Article
• Language: English
• Published: Brazil Springer Nature B.V 01-03-2015; Sociedade Brasileira de Microbiologia
• Subjects: Animals; Bacteria; Brazil; Enzyme Stability; Enzymes; Escherichia coli - genetics; Escherichia coli - metabolism; Food Microbiology; Hydrogen-Ion Concentration; Lipase - chemistry; Lipase - genetics; Lipase - isolation & purification; Lipase - metabolism; MICROBIOLOGY; Milk; Milk - microbiology; Peptide Hydrolases - chemistry; Peptide Hydrolases - genetics; Peptide Hydrolases - isolation & purification; Peptide Hydrolases - metabolism; Proteases; Pseudomonas fluorescens - genetics; Pseudomonas fluorescens - isolation & purification; Recombinant Proteins - chemistry; Recombinant Proteins - genetics; Recombinant Proteins - isolation & purification; Recombinant Proteins - metabolism; Refrigeration; Substrate Specificity; Temperature; Brazil; Pseudomonas fluorescens; raw milk; extracellular lipase; food deterioration; extracellular protease
• ISSN: 1678-4405; 1517-8382; 1678-4405
• DOI: 10.1590/S1517-838246120130859

The practice of refrigerating raw milk at the farm has provided a selective advantage for psychrotrophic bacteria that produce heat-stable proteases and lipases causing severe quality problems to the dairy industry. In this work, a protease (AprX) and a lipase (LipM) produced by Pseudomonas fluorescens 041, a highly proteolytic and lipolytic strain isolated from raw milk obtained from a Brazilian farm, have been purified and characterized. Both enzymes were purified as recombinant proteins from Escherichia coli . The AprX metalloprotease exhibited activity in a broad temperature range, including refrigeration, with a maximum activity at 37 °C. It was active in a pH range of 4.0 to 9.0. This protease had maximum activity with the substrates casein and gelatin in the presence of Ca (+2) . The LipM lipase had a maximum activity at 25 °C and a broad pH optimum ranging from 7.0 to 10. It exhibited the highest activity, in the presence of Ca (+2) , on substrates with long-chain fatty acid residues. These results confirm the spoilage potential of strain 041 in milk due to, at least in part, these two enzymes. The work highlights the importance of studies of this kind with strains isolated in Brazil, which has a recent history on the implementation of the cold chain at the dairy farm.