Studies on the catalytic behavior of a membrane-bound lipolytic enzyme from the microalgae Nannochloropsis oceanica CCMP1779

Abstract The catalytic behavior of a membrane-bound lipolytic enzyme (MBL-Enzyme) from the microalgae Nannochloropsis oceanica CCMP1779 was investigated. The biocatalyst showed maximum activity at 50 °C and pH 7.0, and was stable at pH 7.0 and temperatures from 40 to 60 °C. Half-lives at 60 °C, 70 °C and 80 °C were found 866.38, 150.67 and 85.57 min respectively. Thermal deactivation energy was 68.87 kJ mol −1 . The enzyme’s enthalpy (Δ Η *), entropy (Δ S *) and Gibb’s free energy (Δ G *) were in the range of 65.86–66.27 kJ mol −1 , 132.38–140.64 J mol −1  K −1 and 107.80–115.81 kJ mol −1 , respectively. Among p -nitrophenyl esters of fatty acids tested, MBL-Enzyme exhibited the highest hydrolytic activity against p -nitrophenyl palmitate ( p NPP). The K m and V max values were found 0.051 mM and of 0.054 mmole p NP mg protein −1  min −1 , respectively with p NPP as substrate. The presence of Mn 2+ increased lipolytic activity by 68.25%, while Fe 3+ and Cu 2+ ions had the strongest inhibitory effect. MBL-Enzyme was stable in the presence of water miscible (66% of the initial activity in ethanol) and water immiscible (71% of the initial activity in n -octane) solvents. Myristic acid was found to be the most efficient acyl donor in esterification reactions with ethanol. Methanol was the best acyl acceptor among the primary alcohols tested.