Extraction of lipase enzymes from rice bran and rapid isolation of thermostable lipase by thermal denaturation of other proteins

Abstract

Oryza sativa (rice) is a main component of the diet of almost half of people globally. Rice bran is a byproduct of milling rice. Three lipases have been reported in rice bran; Lipase I, Lipase II and thermostable lipase, all of which were reported to contribute to the short shelf life of rice bran due to rancidity. Thermostable lipase has an optimum activity at 80°C and reportedly maintains most of its secondary protein structure at 90°C. Extraction and isolation of the thermostable lipase in rice bran will add value to this byproduct of the rice industry due to potential applications in the detergent industry at high temperatures, precisely to remove lipid stains. We report rapid isolation of the thermostable lipase from rice bran by thermal denaturation of other proteins. Rice bran was defatted, and proteins were extracted using 50 mM Tris-HCl buffer at pH 8.0 before thermal denaturation of other proteins at 80°C and 100°C to isolate the thermostable lipase rapidly. The lipase concentration in the thermally denatured sample was measured using phenylacetate assay as the lipase activity assay, measuring the absorbance at 765 nm via a spectrophotometer. The protein yield in g per kg of dry weight of rice bran for thermostable lipase were 3.05 ± 0.03 and 2.7 ± 0.01 at 80 °C and 100 °C respectively. The results indicate the activity of thermostable lipase in rice bran at both temperatures.