Immobilization of enantioselective lipase on soluble supports for kinetic resolution of drug intermediates

The microbial lipase, Arthrobacter sp. lipase (MTCC 5125), from the Indian Institute of Integrative Medicine repository, is known as an effective catalyst for high enantioselective kinetic resolution of drug intermediates. The ABL was immobilized on water-soluble linear supports by covalently binding it to the epoxy groups on the N-vinyl pyrrolidone/allyl glycidyl ether and N-vinyl pyrrolidone/glycidyl methacrylate copolymers. The immobilized lipase, on different soluble supports, had 90–110 mg/g protein binding and 500–700 U/g hydrolysis activities for tributyrin substrate. These copolymers had soluble/insoluble characteristics in different pH ranges, which is an advantage over insoluble copolymers. A soluble polymer at neutral pH provided better accessibility to the immobilized enzyme, which was recovered by precipitation at pH 2–3 for reuse. Kinetic resolution of racemic acyl derivatives of chiral auxiliaries and drug intermediates, namely, phenyl ethanol, aminoalcohol, and fluoxetine intermediate resulted in a significant enhancement in enantioselectivity (99%).

Immobilization of Lipase by Entrapment in Ca-alginate Beads

The lipase-producing strain, Arthrobacter sp. (ABL), isolated was immobilized in Ca-alginate beads by entrapment. The alginate beads were prepared as an aqueous mixture of sodium alginate, the cells and CaCl2 to increase its reusability, and overall enzyme stability. Various parameters like alginate and CaCl2 concentration, lipase units loading and bead size were evaluated for optimum immobilization yield. It was observed that with the increase in alginate concentration, the yield of immobilized enzyme also increased up to a limit. A similar pattern was observed with CaCl2 addition; the optimum concentrations of alginate and CaCl2 observed were 1.5% (w/v) and 2%, respectively. The concentration of enzyme entrapped in the beads with an activity of 5 units per gram of wet beads was obtained by the addition of 100 units in 10 mL of slurry; beyond this amount a very little increase in activity was observed. The maximum immobilization yield was observed with a 1.2 mm bead size; increased bead sizes decreased the yield of immobilization. After optimization of all the parameters, a 40% yield of lipase (ABL) activity was observed in the Ca-alginate beads. These lipase beads were used for 10 cycles for the hydrolysis of triglycerides without any loss in activity. The entrapped lipase was more stable over a wide range of temperatures, pH, and storage time as compared to free enzyme.