title: Immobilization and stability of lipase from Mucor racemosus NRRL 3631.
abstract: The lipase from Mucor racemosus NRRL 3631 was 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 45 degrees Celsius. The calculated half-lives (472.5, 433.12, and 268.5 min at 50, 55, and 60 degrees Celsius, 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 K(m) (11.11 mM) and lower V(max) (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.
authors.affiliation: Chemistry of Natural and Microbial Products Department, National Research Centre, Dokki, Cairo, Egypt. nehadhnrc@yahoo.com
authors.forename: Nehad Zaki
authors.initials: NZ
authors.lastname: Adham
authors.forename: Hanan Mostafa
authors.initials: HM
authors.lastname: Ahmed
authors.forename: Nadia
authors.initials: N
authors.lastname: Naim
mesh_terms: D004800:Enzymes, Immobilized / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D005656:Fungal Proteins / Q000737:chemistry* / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D007700:Kinetics; D008049:Lipase / Q000737:chemistry* / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D009089:Mucor / Q000737:chemistry / Q000201:enzymology* / Q000235:genetics; D055550:Protein Stability; D013379:Substrate Specificity
chemical_list: D004800:Enzymes, Immobilized; D005656:Fungal Proteins; D008049:Lipase