Identification of heat stable protease of Klebsiella oxytoca isolated from raw milk |
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Authors: | Tondo E C Lakus F R Oliveira F A Brandelli A |
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Institution: | Departamento de Ciência de Alimentos, ICTA, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil. |
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Abstract: | AIMS: The aim of this study was to identify and characterize heat stable proteinases of psychrotrophic proteolytic bacteria isolated from raw milk. METHODS AND RESULTS: A strain of Klebsiella oxytoca producing a high proteolytic activity when cultured on milk was isolated. Maximum proteolytic activity was observed at the stationary phase during growth on milk or casein-peptone broth. The bacterium demonstrated the capability to grow at 7 degrees C, classified as psychrotrophic. The crude enzyme showed optimum activity at 37 degrees C, and pH 5.0 and 7.0. The proteinase was very resistant to heat, maintaining 74% of initial activity after incubation at 142 degrees C. CONCLUSIONS: A heat stable protease of a psychrotrophic strain of K. oxytoca was identified and partially characterized. SIGNIFICANCE AND IMPACT OF THE STUDY: Thermal stable proteases may constitute a serious problem to ultra-high temperature (UHT) processed milk, leading to undesirable physical and sensory alterations. |
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Keywords: | enzyme Klebsiella oxytoca milk proteolysis UHT |
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