Abstract:Effects of different types and concentrations of surfactants on the lipase/ activity and phospholipase activity of the Gibberella Zeae lipase (GZEL) and its corresponding optimum pH were examined by automatic potentiometric titration, to provide scientific guidance for further evaluation on the application potential of the lipase in the detergent industry. Results revealed that both anionic and cationic surfactants exerted inhibitory effects on the lipase activity and phospholipase activity of GZEL, and the inhibition increased with an increase of the surfactant concentration, with a surfactant concentration higher than its critical micelle concentration causing the complete loss of the activity of the enzyme protein. In the presence of an anionic surfactant (sodium N-lauroylsarcosinate, sodium dodecyl sulfate (SDS), sodium taurodeoxycholate (NATDC), the optimal pH for the phospholipase activity of GZEL was changed from pH 6.0 to pH 7.0. Different nonionic surfactants had different effects on both activities of GZEL at concentrations lower than their corresponding critical micelle concentrations: At a concentration of 7.0 mM, octyl-β-d-glucopyranoside increased the lipase activity (by 22.97%) and phospholipase activity (by 3.11%) of GZEL, whereas, at 0.05 mM, Triton X-100 reduced the lipase activity (by 4.05%) of GZEL, but increased the phospholipase activity (0.14%) of GZEL. When the concentration of Triton X-100 was higher than its critical micelle concentration, GZEL about 50% of the enzyme activity was still retained, whereas, octyl-β-d-glucopyranoside at a concentration higher than its critical micelle concentration made the activity of GZEL lose completely. Zwitterionic surfactant had the greatest effect on the activity of GZEL, resulting in the complete inactivation of enzyme protein.
