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KMID : 0545120100200020332
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Journal of Microbiology and Biotechnology
2010 Volume.20 No. 2 p.332 ~ p.339
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Immobilization and stability of lipase from Mucor racemosus NRRL 3631
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Adham Nehad Zaki
Hanan Mostafa Ahmed
Nadia Naim
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Abstract
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The lipase from Mucor racemosus NRRL 3631was partially purified by fractional precipitation using 60% ammonium sulfate, which resulted in a 8.33-fold purification. The partially purified lipase was then immobilized using different immobilization techniques: physical adsorption, ionic binding, and entrapment. Entrapment in a 4% agar proved to be the most suitable technique (82% yield), as the immobilized lipase was more stable at acidic and alkaline pHs than the free enzyme, plus 100% of the original activity was retained owing to the thermal stability of the immobilized enzyme after heat treatment for 60 min at 45oC. The calculated half-lives (472.5, 433.12, and 268.5min at 50, 55, and 60oC, respectively) and the activation energy (9.85 kcal/mol) for the immobilized enzyme were higher than those for the free enzyme. Under the selected conditions, the immobilized enzyme had a higher Km (11.11 mM) and lower Vmax (105.26 U/mg protein) when compared with the free enzyme (8.33 mM and 125.0 U/mg protein, respectively). The operational stability of the biocatalyst was tested for both the hydrolysis of triglycerides and esterification of fatty acids with glycerol. After 4 cycles, the immobilized lipase retained approximately 50% and 80% of its original activity in the hydrolysis and esterification reactions, respectively.
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KEYWORD
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Lipase, Enzyme immobilization, Agar, Stabilization, Mucor racemosus
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