Immobilization of lipase from Candida rugosa on novel phosphorous-containing polyurethanes: Application in wax ester synthesis

We have synthesized five novel phosphorous-containing polyurethanes using a two-step procedure. The materials have been characterized using small-angle X-ray scattering, 1H NMR and IR analysis and applied as carriers for Candida rugosa lipase (CRL–PU preparations). We achieved high yields (75–97.3%) of cetyl palmitate for 5 h in a solvent-free medium with CRL–PUs. Pre-treatment of the supports with polar or non-polar solvents had a negative effect on the lipase loading. Non-ionic surfactants have increased the immobilization yield of CRL by 30–40% as well as the hydrolytic activity of the preparations. The additives, however, had a negligible effect on their synthetic activity. Not surprisingly, the immobilization improved the enzyme thermal stability. In aqueous media at 55 °C, CRL–PU1 completely preserves its activity and at higher temperatures is even twice more active than the native enzyme. It has a half-life of 70 h at 55 °C. Applied in the esterification of palmitic acid with cetyl alcohol, the biocatalyst retained 80% of its original activity after fifteen subsequent 5-h cycles. The highest synthetic activity of CRL–PU1 preparations was observed at a w = 0.33. As expected, polar solvents destabilize the immobilized C. rugosa lipase. Hexadecane enhance both hydrolytic and synthetic activities of CRL–PU1. They are active in a wide range of solvents varying in their polarity (log P from −1.3 to 8.8).