Enzymes extract proteins from rice bran efficiently.

Proteins found in heat-stabilized and defatted rice bran (HDRB) are difficult to extract. Heating decreases the solubility of proteins through denaturation and complexing with other components. New efficient ways to extract these proteins could add value to rice bran.

Enzyme-aided approaches could preserve the functionality of proteins while improving extraction efficiency. Enzymatic techniques require gentle conditions and extract proteins that are otherwise insoluble. Scientists at the University of Arkansas evaluated the role of selected enzymes in hydrolyzing proteins. They characterized peptides from the rice bran matrix.

The investigators studied five enzymes, including a xylanase, a fungal protease, proteinase A, Econase CEP and a umamizyme protease. Rice bran proteins were extracted using aqueous solutions with these enzymes at their optimum conditions. The protein contents of the extracts were determined, and extracted proteins were characterized using gel electrophoresis.

There was a 128% increase in the amount of protein extracted with proteinase A (10,000 U/100 g rice bran) treatment, compared to the control. There were 15%, 5%, 39% and 62 % increases in the amount of protein extracted using xylanase (3,000,000 U), fungal protease (500,000 U), Econase CEP (100,000 U) and Umamizyme (70 U), respectively, in 100 g of rice bran.

Gel electrophoresis indicated that proteinase A-treated proteins showed major bands at 55, 46, 27 and 20 kDa. Umamizyme protease-treated proteins showed major bands at around 35 and 12 kDa. Fungal protease-extracted proteins showed major bands at 38 and 28 kDa. Econase CEP- and xylanase-treated proteins showed bands below 15 kDa.

The results suggest that enzyme-aided procedures extracted more proteins than the controls, with proteinase A being most effective. Enzymes produced different polypeptide segments not observed with the controls, suggesting that the release of these peptides from the rice bran matrix occurred through enzymatic hydrolysis.

Further information. S. Hettiarachchy, Department of Food Science, University of Arkansas, N-218, 2650 N. Young Ave., Fayetteville, AR 72704; phone: [phone]; fax: [phone]; email: [e-mail].