ummary
The stability of crude extracellular protease produced by Bacillus licheniformis RP1,
isolated from polluted water, in various solid laundry detergents was investigated.
The enzyme had an optimum pH and temperature at pH 10.0–11.0 and 65–70 1C.
Enzyme activity was inhibited by PMSF, suggesting that the preparation contains a
serine-protease. The alkaline protease showed extreme stability towards non-ionic
(5% Tween 20% and 5% Triton X-100) and anionic (0.5% SDS) surfactants, which
retained 100% and above 73%, respectively, of its initial activity after preincubation
60 min at 40 1C.
The RP1 protease showed excellent stability and compatibility with a wide range
of commercial solid detergents at temperatures from 40 to 50 1C, suggesting its
further application in detergent industry. The enzyme retained 95% of its initial
activity with Ariel followed by Axion (94%) then Dixan (93.5%) after preincubation
60 min at 40 1C in the presence of 7 mg/ml of detergents. In the presence of Nadhif
and New Det, the enzyme retained about 83.5% of the original activity. The effects
of additives such as maltodextrin, sucrose and PEG 4000 on the stability of the
enzyme during spray-drying and during subsequent storage in New Det detergent
were also examined. All additives tested enhanced stability of the enzyme.
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