Abstract:

In order to obtain a high activity of acidolysis, Rhizopus oryzae lipase (ROL) was modified with NaIO4-oxidized
dextran. The effects of reaction time, reaction pH, reductant concentration and dextran concentration on modification
efficiency were studied. Box-Behnken experimental design and response surface methodology were used to optimize the
modification conditions as follows: pH 7.63; reaction time, 15.53 h; reductant concentration, 0.20 mol/L; and dextran
concentration, 0.3%. Under these conditions, the maximum predicted acidolysis rate of lipase of 37.28% was obtained, which
was basically consistent with the experimental value. The effect of the above four factors on the acidolysis rate of lipase
was in the decreasing order of reaction time, reaction pH, dextran concentration and reductant concentration. After chemical
modification, ROL had obvious changes in absorption characteristics in the ultraviolet region. The maximum absorption
wavelength was obviously different. At the optimum temperature of 40 ℃, the activity of dextran-ROL was increased
2.2 times compared to ROL, and the stability of dextran-ROL was also improved significantly.

Key words: Rhizopus oryzae lipase, chemical modification, dextran, response surface methodology, acid hydrolysis activity