[Purification and characterization of proteases from Pseudomonas fluorescens and their effects on milk proteins]

The increase in the levels of psychotropic bacteria in the raw milk during the refrigeration period, could lead to the production of heat-resistant enzymes responsible for the deterioration of long-life industrial dairy products. Pseudomonas fluorescens is the psychotropic bacteria most commonly found in milk in Southern Chile. In the present work the enzymatic proteinases extract of cultures of Pseudomonas fluorescens RV10 at 6 degrees C in raw milk just milked were purified. It was found that the proteases corresponds to a protein with a molecular mass of 49.5 kD, that presents heat resistance and rapidly attacks the k-casein continuing with the b-casein. It is possible to conclude that storage of the milk for long-life products at 6 degrees C is risky, as it causes the loss of quality for the proteases of psychotropic bacteria.