Enhanced Nonaqueous Stability of Pseudomonas Cepacia Lipase Immobilized on Phthalocyanine-Dyed Absorbent Cotton

Abstract

To enhance the nonaqueous catalysis of lipases, Pseudomonas cepacia lipase was immobilized on cotton fibers dyed with tetra-β-amino-phthalocyanine zinc or tetra-β-nitro-phthalocyanine zinc by physical adsorption in a column glass bottle and used to catalyze transesterification between hexanol and vinyl acetate. The suitable ratios of lipase to immobilized carriers were 10: 10 (mg: mg), and the employed carriers enhanced the enzymatic activity by more than 2.3-fold during the initial reaction stage. When the immobilized lipases were subjected to repeated uses at 37 °C and 160 rpm, their nonaqueous stability followed this order: cotton dyed with tetra-β-amino-phthalocyanine zinc > cotton fibers > cotton dyed with tetra-β-nitro-phthalocyanine zinc. The decrease in their substrate conversion efficiency after 24 h was 5.7%, 24.7%, and 33.3%, respectively, indicating that tetra-β-amino-phthalocyanine zinc provides effective protection for the enzyme.