Abstract:Rice bran lipase can make rice bran go rancid, and conventional heat treatment methods are difficult to completely inactivate endogenous lipase in rice bran. In order to evaluate the presence of heat-resistant lipase in rice bran, the present study was carried out to investigate the effects of surfactant type and concentration on the lipase activity of rice bran’s crude enzyme solution using the rice bran stabilized by the wet heat treatment as the raw material, and further compare the characteristics of the two lipases, Triton x-100 rice bran lipase (TRBL) and phosphate rice bran lipase (PRBL). The lipase activity of the crude enzyme solution extracted with 10 mmol/L surfactant increased significantly, with the Triton x-100 group exhibiting the best effect. Comparison on the properties of TRBL and PRBL revealed that the optimal reaction temperature and pH of PRBL were 30 ℃ and 7.0, respectively, whilst the optimal reaction temperature of TRBL was over 100 ℃ and it had good heat resistance, with the optimal reaction pH of being 3.0 and 7.0; The two crude liquid lipases had no significant specificity in the hydrolysis of substrates with different carbon chains; Ba2+ and Zn2+ could activate the lipase activity of the crude liquid enzymes, but the activation effect of Ba2+ on the activity of TRBL was much higher than that of the PRBL group. K+ and Fe3+ had the greatest inhibitory effect on the lipase activities of PRBL and TRBL, respectively; TRBL had better tolerance to organic solvents than PRBL, and methanol had an activating effect on TRBL’s lipase activity. The study proved that there were lipases that could tolerate temperature and organic solvents in stabilized rice bran, which provides a theoretical basis for in-depth exploration of novel rice bran lipases.
