Immobilization of the Candida rugosa lipase onto a Scirpus grossus L.f. fiber as biocatalyst for biodiesel synthesis via hydrolysis-esterification

This study aimed to immobilize the Candida rugosa lipase (C. rugosa lipase) on ground Scirpus grossus L.f. fibers by glutaraldehyde-crosslinking to form a hydrolysis-esterification catalyst for biodiesel synthesis. The effects of different glutaraldehyde concentrations and solvent for 3-aminopropyltriethoxysilane (3-APTES) activation of the fibers on the resultant immobilized lipase activity, protein loading, degree of immobilization and catalytic efficiency were investigated. The optimum condition found was to first activate the S. grossus L.f. fibers using 2% (w/v) of 3-APTES in distilled water and subsequently crosslink with 0.2% (w/v) glutaraldehyde prior to C. rugosa lipase immobilization at pH 7. The immobilized C. rugosa lipase was then evaluated as a biocatalyst for biodiesel synthesis via the hydrolysis-esterification of palm oil and bioethanol through monitoring the production of free fatty acids (FFAs) and fatty acid ethyl ester (FAEE, biodiesel). The reusability of immobilized lipase was also determined. The immobilized C. rugosa lipase yielded a higher hydrolysis-esterification efficiency (that is, FFA and FAEE formation) than that of the free lipase with the immobilized form looking promising for FAEE biodiesel production. The C. rugosa lipase immobilized with 0.2% (w/v) glutaraldehyde exhibited the highest reuse stability, retaining some hydrolysis and esterification activity for up to six uses, whereas crosslinking with higher [0.5% or 0.8% (w/v)] glutaraldehyde levels resulted in a loss of both activities within four uses. Key words: Immobilization, lipase, Scirpus grossus L.f. fiber, 3-aminopropyltriethoxysilane, glutaraldehyde, biodiesel.