An Investigation of Proteolytic, Lipolytic Activity and Biofilm Formation by Psychrotrophic Bacteria Isolated from Buffalo Milk

The aim of this study was to investigate the enzymatic activity of 21 bacteria isolated from refrigerated raw buffalo milk, as well as to evaluate the production of biofilm by these bacteria. Proteolytic, lipolytic and lecithinase activity, as well as the production of exopolysaccharides were evaluated at different temperatures. For all of the psychrotrophic bacteria, biofilm formation on microtiter plates was evaluated at different temperatures and in the presence of residual buffalo and bovine milk. All cultures showed a proteolytic profile while 9 cultures showed lipase activity. Lecithinase production was found in 7 of the evaluated psychrotrophic bacteria. The ability to produce exopolysaccharides was found in 12 bacteria. Of the 21 bacterial isolates, 16 were biofilm producers at 7°C. At 23°C, 20 isolates were found to be biofilm producers. At a temperature of 37°C, biofilm formation by 17 isolates was weak. In the presence of residual buffalo milk, 7 were biofilm producers, while 16 bacteria produced biofilm in residual bovine milk. The results of this study show that many isolates of psychrotrophic bacteria from raw buffalo milk have the potential to produce extracellular enzymes as well as biofilm. This deserves special attention when considering the best practices to recommend during the collection of raw milk in establishments which process milk

Thermal resistance of proteolytic enzymes produced by psychrotrophic bacteria isolated from buffalo milk

Background and Objective: Psychrotrophic bacteria produce extracellular proteases, resulting in deterioration and reduced shelf life of dairy products. In this study, 21 species of psychotropic bacteria isolated from buffalo milk were selected and the thermal resistance of the proteases produced by these bacteria was evaluated. Materials and Methods: The isolates were tested to evaluate proteolytic activity of buffalo milk agar. The cell-free supernatants from the growing of isolates were obtained for the quantification of enzymatic activity under different pH values (5.5, 7.0 and 8.0). Thermal resistance and the clotting ability of proteolytic enzymes in buffalo and bovine milk substrates were also evaluated. One-way ANOVA test with a critical probability of p1 U mLG1 under at least one of the pH tested. Five isolates produced cell-free supernatants resistant to pasteurization (63.5EC/30 min), following which they were able to coagulate buffalo and bovine milk. The crude enzyme of P. fluorescens PL5.4 showed the greatest enzymatic activity within a wide pH range (4-10) and at an optimum temperature of 40EC. The cell-free supernatant of this isolate resisted to tests with detergents and organic solvents. However, it was not possible to identify the type of protease. Conclusion: The results of this study showed the negative impact of the presence of psychrotrophic bacteria producing proteolytic enzymes in buffalo milk. This is because the enzymes studied caused changes in milk samples, revealing a negative impact on the production of derived products. This is significant, since the buffalo milk produced in Brazil is directed to the production of dairy products

Study of the mechanisms related to the formation of biofilmes by Pseudomonas fluorescens isolated of raw milk of buffala

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Thermal resistance of proteolytic enzymes produced by psychrotrophic bacteria isolated from buffalo milk

Background and Objective: Psychrotrophic bacteria produce extracellular proteases, resulting in deterioration and reduced shelf life of dairy products. In this study, 21 species of psychotropic bacteria isolated from buffalo milk were selected and the thermal resistance of the proteases produced by these bacteria was evaluated. Materials and Methods: The isolates were tested to evaluate proteolytic activity of buffalo milk agar. The cell-free supernatants from the growing of isolates were obtained for the quantification of enzymatic activity under different pH values (5.5, 7.0 and 8.0). Thermal resistance and the clotting ability of proteolytic enzymes in buffalo and bovine milk substrates were also evaluated. One-way ANOVA test with a critical probability of p1 U mLG1 under at least one of the pH tested. Five isolates produced cell-free supernatants resistant to pasteurization (63.5EC/30 min), following which they were able to coagulate buffalo and bovine milk. The crude enzyme of P. fluorescens PL5.4 showed the greatest enzymatic activity within a wide pH range (4-10) and at an optimum temperature of 40EC. The cell-free supernatant of this isolate resisted to tests with detergents and organic solvents. However, it was not possible to identify the type of protease. Conclusion: The results of this study showed the negative impact of the presence of psychrotrophic bacteria producing proteolytic enzymes in buffalo milk. This is because the enzymes studied caused changes in milk samples, revealing a negative impact on the production of derived products. This is significant, since the buffalo milk produced in Brazil is directed to the production of dairy products