Pseudomonas cepacia lipase immobilized onto expandable polystyrene beads for biodiesel production

Abstract

In previous results of our research group, the lipase from Pseudomonas cepacia was immobilized onto polyglutaraldehyde-styrene copolymer coated expandable polystyrene beads (PGlu-STY/EPS) with only one particle size. There was a report that the maximum enzymatic reaction rate was at a higher level by using lipase-immobilizing with smaller particle size. To improve the efficiency of lipase-immobilized catalyst for biodiesel production, the smaller particle sizes of PGlu-STY/EPS beads were prepared by varying coating temperature and the beads prepared however were unsuitable for immobilization of the lipase. Thus two sizes of expandable polystyrene bead (EPS) consisting of EPS bead grade 291L, with size of 1.00-1.60 mm, and EPS bead grade 321F, with size of 0.63-1.12 mm, were used for coating with PGlu-STY copolymer and the lipase-immobilized catalysts were then evaluated their lipase activity and efficiency for biodiesel production from soybean oil. During coating process, it was found that PGlu-STY/EPS beads not only could be prepared by using soluble polyglutaraldehyde as described in the literature but also the whole suspension of polyglutaraldehyde generated from the same original concentration of the glutaraldehyde. Using the whole suspension of polyglutaraldehyde gave the higher percentage of coating PGlu-STY on both sizes of EPS beads than that of soluble polyglutaraldehyde. In both sizes of EPS beads, the lipase-immobilized catalysts that was prepared by using the soluble polyglutaraldehyde provides higher activity than that was prepared by using the whole suspension of polyglutaraldehyde and the activity of lipase immobilized on 321FEPS bead was higher than 291LEPS bead. The efficiency of those immobilized catalysts for biodiesel production from soybean oil was notably low. Nevertheless, the addition of water to the reaction could significantly improve production of biodiesel. Furthermore, the lipase-immobilizing with small size which was prepared by using the soluble and the whole polyglutaraldehyde has better efficiency than the bigger one.