T1 lipase was incubated with nonionic, cationic (CTAB), anionic (N-L and sodium dodecyl sulphate [SDS]), and zwitterionic (SB3-14) surfactants at different concentrations, and subsequent changes in enzymatic activity was measured using p-nitrophenyl dodecanoate as substrate. The results showed that nonionic surfactants at low concentrations activated T1 lipase, whose relative activity increased by 50% to 150%. Conversely, T1 lipase activity was inhibited to various degrees when the concentration of nonionic surfactants exceeded their critical micelle concentration, and the most significant inhibitory effect was observed with Tween 80. The cationic, anionic, and zwitterionic surfactants strongly inhibited T1 lipase activity, probably due to strong charge repulsions produced between the charged groups of the surfactant and the charged amino acids on the protein surface, which may have led to protein denaturation and inactivation. On the other hand, SDS and SB3-14 at low concentrations slightly activated T1 lipase. Since T1 lipase is a thermostable lipase with high industrial application value, it would be useful to further investigate the effects of different surfactants on T1 lipase activity to help select suitable surfactants for different purposes.
