Treatment of oat bran with carbohydrases increases soluble phenolic acid content and influences antioxidant and antimicrobial activities

This study examined antioxidant and antimicrobial activities of medium oat bran treated with four polysaccharide enzymes viscozyme, cellulase, alpha-amylase, and amyloglucosidase. The effects of these enzymes on the release of phenolic acids were determined using reverse-phase HPLC chromatography. Antioxidant assays showed that enzyme pre-treatments significantly increased the hydroxyl radical (HO center dot) scavenging activity of all bran samples (16.6-20.0 mu M propyl gallate equivalents (PGE)/g bran) relative to untreated bran (13.3 +/- 1.8 mu M PGE/g). The order of activity was cellulase approximate to viscozyme > amyloglucosidase approximate to alpha-amylase. The DPPH free radical inhibitory activities of brans pre-treated with cellulase and amyloglucosidase, 43.0% and 45.0%, respectively were higher than inhibition by untreated bran 21.7% (P < 0.05). In the linoleic acid (LA) autoxidation assay, three of the treated and untreated brans similarly inhibited LA oxidation, while viscozyme pre-treated bran had no activity. HPLC analysis showed an increase in free phenolic acids, and this was more pronounced for ferulic and caffeic acids. In the antimicrobial assay, brans pre-treated with viscozyme and cellulase similarly inhibited the growth of Escherichia coli compared to untreated bran (P < 0.05), while viscozyme- and alpha-amylase-treated brans enhanced the growth of Bacillus subtilis, a non-pathogenic bacteria strain that has been used as a pro-biotic. (C) 2013 Elsevier Ltd. All rights reserved.