Catalytic potential of a poly(AAc‐ co ‐HPMA‐ cl MBAm)‐matrix‐immobilized lipase from a thermotolerant Pseudomonas aeruginosa MTCC‐4713

A purified alkaline thermo‐tolerant lipase from Pseudomonas aeruginosa MTCC‐4713 was immobilized on a series of five noble weakly hydrophilic poly(AAc‐ co ‐HPMA‐ cl MBAm) hydrogels. The hydrogel synthesized by copolymerizing acrylic acid and 2‐hydroxy propyl methacrylate in a ratio of 5 : 1 (HG 5:1 matrix) showed maximum binding efficiency for lipase (95.3%, specific activity 1.96 IU mg −1 of protein). The HG 5:1 immobilized lipase was evaluated for its hydrolytic potential towards p ‐NPP by studying the effect of various physical parameters and salt‐ions. The immobilized lipase was highly stable and retained ∼92% of its original hydrolytic activity after fifth cycle of reuse for hydrolysis of p ‐nitrophenyl palmitate at pH 7.5 and temperature 55°C. However, when the effect of pH and temperature was studied on free and bound lipase, the HG 5:1 immobilized lipase exhibited a shift in optima for pH and temperature from pH 7.5 and 55°C to 8.5 and 65°C in free and immobilized lipase, respectively. At 1 m M concentration, Fe 3+ , Hg 2+ , NH 4 + , and Al 3+ ions promoted and Co 2+ ions inhibited the hydrolytic activities of free as well as immobilized lipase. However, exposure of either free or immobilized lipase to any of these ions at 5 m M concentration strongly increased the hydrolysis of p ‐NPP (by ∼3–4 times) in comparison to the biocatalysts not exposed to any of the salt ions. The study concluded that HG 5:1 matrix efficiently immobilized lipase of P. aeruginosa MTCC‐4713, improved the stability of the immobilized biocatalyst towards a higher pH and temperature than the free enzyme and interacted with Fe 3+ , Hg 2+ , NH 4 + , and Al 3+ ions to promote rapid hydrolysis of the substrate ( p ‐NPP). © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 4252–4259, 2006