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 °C, and pH 8.0, 40–50 °C, respectively. PECp-lipase maintained 100% of initial activity after 35 days of storage at room temperature. The thermal kinetic parameters (kd and t1/2) and Ed evidenced that immobilization provide higher thermal stability to PECp-lipase compared to free enzyme. Thermodynamic parameters (ΔH°, ΔS° and ΔG°) 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.