Properties of poly(AAc-co-HPMA-cl-EGDMA) hydrogel-bound lipase of Pseudomonas aeruginosa MTCC-4713 and its use in synthesis of methyl acrylate

摘要

Microbial lipases (E.C. 3.1.1.3) are preferred biocatalysts for the synthesis of esters in organic solvents. Various extracellular thermoalkaliphilic lipases have been reported from Pseudomonas sp. In the present study, a purified alkaline thermoalkalophilic extracellular lipase of Pseudomonas aeruginosa MTCC-4713 was efficiently immobilized onto a synthetic poly(AAc-co-HPMA-cl-EGDMA) hydrogel by adsorption and the bound lipase was evaluated for its hydrolytic potential towards various p-nitrophenyl acyl esters varying in their C-chain lengths. The bound lipase showed optimal hydrolytic activity towards p-nitrophenyl palmitate (p-NPP) at pH 8.5 and temperature 45 degrees C. The hydrolytic activity of the hydrogel-bound lipase was markedly enhanced by the presence of Hg2+, Fe3+, and NH4+ salt ions in that order. The hydrogel-immobilized lipase (25 mg) was used to perform esterification in various n-alkane(s) that resulted in similar to 84.9 mM of methyl acrylate at 45 degrees C in n-heptane under shaking (120 rpm) after 6 h, when methanol and acrylic acid were used in a ratio of 10 mM:100 mM, respectively. Addition of a molecular sieve (3 angstrom x 1.5 mm) to the reaction system at a concentration of 100 mg/reaction vol (1 mL) resulted in a moderate enhancement in conversion of reactants into methyl acrylate (85.6 mM). During the repetitive esterification under optimum conditions, the hydrogel-bound lipase produced 71.3 mM of ester after 10th cycle of reuse. (c) 2007 Wiley Periodicals, Inc.