title: Physical immobilization of Rhizopus oryzae lipase onto cellulose substrate: activity and stability studies.
abstract: Rhizopus oryzae lipase (ROL) was immobilized by adsorption onto oxidized cellulose fibers and regenerated films. The maximum adsorption level increases with the raise in the amount of carboxylic groups on cellulose surface confirming that adsorption is being governed mainly by electrostatic interaction between the enzyme and the substrate. This hypothesis was further confirmed by zeta-potential measurements showing a decrease in the zeta-potential of the fibers after enzyme adsorption. XPS analysis showed an intensification of the N 1s peak attesting the presence of the enzyme on the surface. The effect of temperature, pH and solvent polarity on the immobilized enzyme activity and stability was investigated. The catalytic esterification of oleic acid with n-butanol has been carried on using hexane as an organic solvent. A high conversion yield was obtained (about 80%) at 37 degrees C with a molar ratio of oleic acid to butanol 1:1 and 150IU immobilized lipase. The adsorption achieved two successive cycles with the same efficiency, and started to lose its activity during the third cycle.
authors.affiliation: Laboratoire de Biochimie et de Génie Enzymatique des Lipases, ENIS route de Soukra, Sfax, Tunisia.
authors.forename: Maha
authors.initials: M
authors.lastname: Karra-Châabouni
authors.forename: Ines
authors.initials: I
authors.lastname: Bouaziz
authors.forename: Sami
authors.initials: S
authors.lastname: Boufi
authors.forename: Ana Maria
authors.initials: AM
authors.lastname: Botelho do Rego
authors.forename: Youssef
authors.initials: Y
authors.lastname: Gargouri
mesh_terms: D020001:1-Butanol / Q000737:chemistry; D000327:Adsorption; D002236:Carbohydrate Conformation; D002384:Catalysis; D002482:Cellulose / Q000737:chemistry*; D004795:Enzyme Stability; D004800:Enzymes, Immobilized / Q000737:chemistry*; D004952:Esters / Q000138:chemical synthesis / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008049:Lipase / Q000737:chemistry*; D008567:Membranes, Artificial; D009829:Oleic Acids / Q000737:chemistry; D012233:Rhizopus / Q000201:enzymology*; D012997:Solvents / Q000737:chemistry; D055672:Static Electricity; D013499:Surface Properties; D013696:Temperature; D013997:Time Factors
chemical_list: D004800:Enzymes, Immobilized; D004952:Esters; D008567:Membranes, Artificial; D009829:Oleic Acids; D012997:Solvents; D020001:1-Butanol; D002482:Cellulose; D008049:Lipase