Lipase immobilized by different techniques on various support materials applied in oil hydrolysis

Abstract

Batch hydrolysis of olive oil was performed by Candida rugosa lipase immobilized on Amberlite IRC-50 and Al2O3. These two supports were selected out of 16 carriers: inorganic materials (sand, silica gel, infusorial earth Al2O3), inorganic salts (CaCO3, CaSO4), ion-exchange resins (Amberlite IRC-50 and IR-4B, Dowex 2X8), a natural resin (colophony), a natural biopolymer (sodium alginate), synthetic polymers (polypropylene, polyethylene) and zeolites. Lipase immobilization was carried out by simple adsorption adsorption followed by cross-linking, adsorption on ion-exchange resins combined adsorption and precipitation, pure precipitation and gel entrapment. The suitability of the supports and techniques for the immobilization of lipase was evaluated by estimating the enzyme activity, protein loading immobilization efficiency and reusability of the immobilizates. Most of the immobilizates exhibited either a low enzyme activity or difficulties during the hydrolytic reaction. Only those prepared by ionic adsorption on Amberlite IRC-50 and by combined adsorption and precipitation on Al2O33 showed better activity, 2000 and 430 U/g support, respectively, and demonstrated satisfactory behavior when used repeatedly. The hydrolysis was studied as a function of several parameters: surfactant concentration, enzyme concentration, pH and temperature. The immobilized preparation with Amberlite IRC-50 was stable and active in the whole range of pH (4 to 9) and temperature (20 to 50 ?C), demonstrating a 99%degree of hydrolysis. In repeated usage, it was stable and active having a half-life of 16 batches which corresponds to an operation time of 384 h. Its storage stability was remarkable too, since after 9 months it had lost only 25 % of the initial activity. The immobilizate with Al2O3 was less stable and less active. At optimal environmental conditions, the degree of hydrolysis did not exceed 79 %. In repeated usage, after the fourth batch, the degree of hydrolysis was reduced to 53.5 %.