Detection of protease and lipase activity in Pseudomonas fluorescens isolated from milk and surfaces as milk deteriorating indicators

Raw milk exposure to many sources of contamination and cold storage is a big problem and may impact milk quality, especially the psychotropic Pseudomonas fluorescens a predominant bacterium causing milk spoilage. Some P. fluorescens strains can produce protease and lipase exoenzymes accelerating the milk spoilage process and reducing the shelf-life of milk and dairy products. Thirty-nine isolates of P. fluorescens isolated from raw cow milk, teat surfaces and milk tanks were examined to detect their abilities to produce both protease and lipase enzymes. These enzymes may increase the virulence of this bacterium based on the detection of both aprX (1434bp) and lip (1422bp) genes using polymerase chain reaction. Results of this study revealed the detection of the aprX gene in (36.8%) of P. fluorescens isolates from raw milk and (81.8%) in bacterium isolated from teat surfaces However, their ability to produce lipase enzymes was reduced by detecting lip genes in (26.3%, 9.1%, and 33.3%) of P. fluorescens isolates from milk, teat surfaces and milk tanks respectively.Theses results confirm the potential of P. fluorescens to induce spoilage in milk and dairy products processed from milk through protease secretion which causes casein hydrolysis and indicates prognosis about the hygienic procedures during milking and processing affecting the milk shelf-life period.