Cellulolytic and xylanolytic enzyme combinations in the hydrolysis of red rice bran: A disparity in the release of nutraceuticals and its correlation with bioactivities

Abstract

Multienzyme-aided processing is recommended as an effective method for releasing the bioactive compounds bounded to rice bran's cell wall matrix. This study aims to investigate the optimal cellulolytic-xylanolytic enzymes combination (CXC1 = 1.5 + 3 units, CXC2 = 3 + 2 units, CXC3 = 4.5 + 1 units per 2 g bran) for improving the release of nutraceuticals and bioactivities from red rice bran compared to control. The results showed significant (p ≤ 0.05) synergistic activities at CXC2 combination with the highest increase in ferulic acid (253%) in soluble phenolics, p-coumaric acid (66%) in bound phenolics and γ-oryzanol fractions (41%–743%). Bioactivity assays showed that all three enzyme combinations exhibited higher ferric reducing power (∼71%), DPPH• (∼13%), nitric oxide (∼114%) scavenging and inhibition of human LDL oxidation (∼13%–34%). While CXC1 and CXC2 increased superoxide anion (∼153%) and hydroxyl radical (∼44%) scavenging activities. Correlation study showed soluble phenolics, ferulic, caffeic acid and 24-methylenecycloartanyl ferulate, exhibiting positive correlation while protocatechuic acid and γ-tocopherol negative correlation with bioactivities. Thus, applying an optimal cellulolytic-xylanolytic enzyme combination is a potential approach for processing the rice bran into a functional food ingredient.