Abstract: This study investigated the effect of the anionic surfactant sodium starch octenyl succinate (SSOS) on the catalytic characteristics of the lipase Novozym51032. The effect of their interaction on the structure of the enzyme was explored by ultraviolet (UV) spectroscopy, fluorescence spectroscopy, and Fourier transform infrared (FTIR) spectroscopy. The results showed that the presence of 6.0 mg/mL SSOS increased the relative activity of the lipase significantly by 164.99%. Kinetic analysis revealed that at a low mass concentration (1 mg/mL) of SSOS, the Michaelis constant (Km) of the lipase decreased from 4.12 to 3.46 μmol/L, but it increased to 58.82 μmol/L at a higher mass concentration (6 mg/mL), with the maximum reaction rate (Vmax) increasing to 333.00 μmol/(L·min). Fluorescence spectroscopy and FTIR spectroscopy showed that the fluorescence intensity of the lipase gradually weakened with increasing concentration of the surfactant, accompanied by secondary structure transformation of the enzyme from α-helix and β-turn to β-sheet. This suggested that the influence of SSOS on the catalytic characteristics of the lipase was associated with the enzyme’s structural alteration.

Key words: lipase; anionic surfactant; catalytic activity; kinetics; spectral behavior