A pectin-lipase derivative as alternative copolymer for lipase assay

In this study Arabic gum and free lipase were successfully replaced by a lipase immobilized onto pectin (PECp-lipase) for pNP palmitate hydrolysis. Using a Central Composite Rotatable Design the optimum pH and temperature for free and PECp-lipase reaction were established at pH 8.0, 30-40 degrees C, and pH 8.0, 40-50 degrees C, respectively. PECp-lipase maintained 100% of initial activity after 35 days of storage at room temperature. The thermal kinetic parameters (k(d) and t(1/2)) and E-d evidenced that immobilization provide higher thermal stability to PECp-lipase compared to free enzyme. Thermodynamic parameters (Delta H degrees, Delta S degrees and Delta G degrees) confirmed the thermal stability acquired by PECp-lipase and indicated that tridimensional structure was preserved. The apparent Michaelis constant estimated for the PECp-lipase (1.15 mM) was not statistically different from the free enzyme (1.09 mM). PECp-lipase represents a faster, single step and, therefore, a very attractive substitute for the lipase standard methodology of pNP palmitate hydrolysis. (C) 2014 Elsevier B.V. All rights reserved.