Immobilization of Candida rugosa lipase on glutaraldehyde-activated Fe3O4@chitosan as a magnetically separable catalyst for hydrolysis of castor oil

Abstract

In this study, the catalysed hydrolysis of castor oil by Candida rugosa lipase (CRL) immobilized on glutaraldehyde-activated magnetic Fe₃O₄@chitosan was investigated. Magnetic Fe₃O₄ was prepared by hydrothermal method and coated with chitosan (CS). Next, CRL was immobilized on Fe₃O₄@chitosan using glutaraldehyde as a cross-linking reagent. The prepared Fe₃O₄@CS@CRL was confirmed by scanning electron microscopy (SEM), X-ray powder diffraction (XRD), vibrating sample magnetometry (VSM), Fourier transform infrared (FTIR) spectroscopy and thermogravimetric analysis (TGA). The response surface methodology (RSM) based on the Box–Behnken design was used to evaluate and optimize the hydrolysis reaction variables. The optimum reaction conditions for the hydrolysis of castor oil by the Fe₃O₄@CS@CRL heterogeneous catalyst were found to be a water/oil ratio of 1.60:1, pH of 7.05, reaction temperature of 34 °C, and lipase concentration of 3.27%; under these conditions, the hydrolysis conversion of castor oil reached 46.81%. Moreover, the immobilized lipase showed high stability with no appreciable loss in its activity after three consecutive cycles.

Practical applications: RSM was found to be a useful technique for optimizing hydrolysis of castor oil. The high conversion of the hydrolysis of castor oil indicates that the Fe₃O₄@CS@CRL has potential to be used in preparing ricinoleic acid from castor oil. Ricinoleic acid have the potential to be used in printing ink as a pigment and dye disperser, plasticizers, surfactants, lubricants and other valuable products.

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