International Journal of Dairy Science1811-97431811-9751Asian Network for Scientific Information10.3923/ijds.2017.339.347BogoMarciele Lauer CruzKarine Gonzalez RevelloAlvaro Paula Folmer CorreaAna BrandelliAdriano Paula Guedes FrazzonAna de Souza da MottaAmanda 52017125Background 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 p<0.05 followed by the Tukeys test was used to evaluate the results. Results: All strains were able to produce proteolysis in buffalo milk agar; additionally, all cell-free supernatants showed enzymatic activity, with values of >1 U mL1 under at least one of the pH tested. Five isolates produced cell-free supernatants resistant to pasteurization (63.5°C/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 40°C. 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.]]>Han, X., F.L. Lee, L. Zhang and M.R. Guo,2012286106Hussain, I., J. Yan, A.S. Grandison and A.E. Bell,201213514041410Quigley, L., O. O'Sullivan, C. Stanton, T.P. Beresford, R.P. Ross, G.F. Fitzgerald and P.D. Cotter,201337664698Vacheyrou, M., A.C. Normand, P. Guyot, C. Cassagne, R. Piarroux and Y. Bouton,2011146253262Sitohy, M., S. Mahgoub and A. Osman,20114416971702Raats, D., M. Offek, D. Minz and M. Halpern,201128465471Baur, C., M. Krewinkel, B. Kranz, M. von Neubeck and M. Wenning et al.,2015492329Button, P.D., H. Roginski, H.C. Deeth and H.M. Craven,201134229235Bagliniere, F., A. Mateos, G. Tanguy, J. Jardin and V. Briard-Bion et al.,2013Pseudomonas fluorescens F induces their destabilisation.]]>315561Marchand, S., J. de Block, V. de Jonghe, A. Coorevits, M. Heyndrickx and L. Herman,201211133147Bekker, A., P. Jooste, L. Steyn, C. Bothma, A. Hugo and C. Hugo,2016Chryseobacterium joostei or Pseudomonas fluorescens.]]>52101106Ruaro, A., C. Andrighetto, S. Torriani and A. Lombardi,201334106111Daroit, D.J., A.P.F. Correa and A. Brandelli,2009Bacillus sp. P45 isolated from the Amazon basin fish Piaractus mesopotamicus.]]>65358363Nornberg, M.F.B.L., M.L. Mentges, S.T. Silveira, E.C. Tondo and A. Brandelli,2011Burkholderia cepacia strain isolated from refrigerated raw milk showing proteolytic activity and adhesion to stainless steel.]]>78257262Nornberg, M.F.B.L., R.S. Friedrich, R.D. Weiss, E.C. Tondo and A. Brandelli,2010634146Mateos, A., M. Guyard-Nicodeme, F. Bagliniere, J. Jardin and F. Gaucheron et al.,2015Pseudomonas LBSA1 isolated from bulk raw milk, and implications for the stability of UHT milk.]]>497888Teh, K.H., S. Flint, J. Palmer, P. Andrewes, P. Bremer and D. Lindsay,20121572834Menard, O., S. Ahmad, F. Rousseau, V. Briard-Bion, F. Gaucheron and C. Lopez,2010120544551Teh, K.H., S. Flint, J. Palmer, D. Lindsay, P. Andrewes and P. Bremer,201121742747Bagliniere, F., J. Jardin, F. Gaucheron, A.F. de Carvalho and M.C.D. Vanetti,2017Serratia liquefaciens leads to the destabilisation of UHT milk during its storage.]]>683845Zhang, S. and J. Lv,2014Pseudomonads fluorescens BJ-10.]]>5111851190Raj, A., N. Khess, N. Pujari, S. Bhattacharya, A. Das and S.S. Rajan,2012Pseudomonas aeruginosa isolated from dairy effluent sludge and determination of its fibrinolytic potential.]]>2S1845S1851Zambare, V., S. Nilegaonkar and P. Kanekar,2011Pseudomonas aeruginosa MCM B-327: Enzyme production and its partial characterization.]]>28173181Mu, Z., M. Du and Y. Bai,2009Pseudomonas fluorescens Rm12 from raw milk.]]>228725734Daroit, D.J., V. Sant’Anna and A. Brandelli,201116517401753Siti, S.D. and R. Hertadi,2015Pseudomonas stutzeri BK AB-12.]]>16341348Alves, M.P., R.L. Salgado, M.R. Eller, P.M.P. Vidigal and A.F. de Carvalho,2016Pseudomonas fluorescens 07A shows that low temperature treatments are more effective in deactivating its proteolytic activity.]]>9978427851