Identification of heat stable protease of Klebsiella oxytoca isolated from raw milk.
OBJECTIVE
The aim of this study was to identify and characterize heat stable proteinases of psychrotrophic proteolytic bacteria isolated from raw milk.


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.


CONCLUSIONS
Thermal stable proteases may constitute a serious problem to ultra-high temperature (UHT) processed milk, leading to undesirable physical and sensory alterations.
Tondo
E C
EC
Departamento de Ciência de Alimentos, ICTA, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil.
Lakus
F R
FR
Oliveira
F A
FA
Brandelli
A
A
D000818:Animals; D004795:Enzyme Stability; D005516:Food Microbiology; D006863:Hydrogen-Ion Concentration; D041121:Klebsiella oxytoca / Q000201:enzymology* / Q000254:growth & development / Q000302:isolation & purification*; D008892:Milk / Q000382:microbiology*; D010447:Peptide Hydrolases / Q000378:metabolism*; D013696:Temperature
D010447:Peptide Hydrolases