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The Effect of Bioprocessing on the Phenolic Acid Composition and Antioxidant Activity of Wheat Bran

¹School of Pharmaceutical Science and Technology, Tianjin University, Weijin Road, Tianjin 300072, China. ²School of Chemical Engineering and Technology, Tianjin University, Weijin Road, Tianjin 300072, China. ³Corresponding author. Phone: +86 2287401895. E-mail: biochemgao@163.com ⁴School of Chinese Medicine, Tianjin University of Traditional Chinese Medicine, Tianjin 300193, China.

In the present study, bioprocessing with eight microbial strains including Bacillus species, yeasts, and filamentous fungi was evaluated for its potential to improve the phenolic acid composition and antioxidant activity of wheat bran. The soluble free and soluble conjugated fractions of ethanolic extracts of the treated bran samples were compared for their total phenolic contents, phenolic acid composition, and in vitro antioxidant activities. In general, total phenolic content in the soluble free fraction increased significantly, accounting for 241.11 ± 1.25 μg of gallic acid equivalents (GE)/g (Rhizopus oryzae), 230.50 ± 1.05 μg of GE/g (Mucor circinelloides), and 230.19 ± 1.02 μg of GE/g (Saccharomycopsis fibuligera). The phenolic acid composition, especially of the soluble free fraction, was improved most by S. fibuligera (hydroxybenzoic, vanillic, syringic, and trans-ferulic acids), M. circinelloides (chlorogenic acid), and R. oryzae (protocatechuic, trans-coumaric, and benzoic acids). Comparatively, bioprocessing exhibited less effectiveness on conjugated phenolic acid composition. Fermented wheat bran displayed enhanced reducing capacity, superoxide anion radical scavenging activity, and 1,1-diphenyl-2-picrylhydrazyl radical scavenging activity in comparison with the nonfermented sample. The antioxidant activity was significantly correlated to the total phenolic content.