Examining Committee
Dr. Doug Goff, Chair
Dr. Yoshinori Mine, Advisor
Dr. Rong Cao, Co-Advisor
Dr. Iris Joye, Department Member

TITLE: Effects of Solid-State Fermentation on the Phytochemical Composition and Antioxidant Activities of Cereal/Pulse/Oilseed Processing By-Products

ABSTRACT: In this study, the effects of solid-state fermentation (SSF) using seven food-grade microbes (Aspergillus spp., Rhizopus spp., Bacillus subtilis and Saccharomyces cerevisiae) on the phenolic compositions and antioxidant activities of low-value brans/hulls, including wheat bran, pea hull and mustard bran, were investigated. Brans/hulls were fermented at optimal incubation temperatures per treatment group (30, 30, 37 and 33 oC) and were collected over a 7-day period (0, 1, 2, 3, 4 and 7 days). Significant enhancement (p<0.05) of total phenolic (TPC) and total flavonoid contents of all bran/hull samples were observed after SSF, depending on the fermentation duration and treatment group. SSF also led to significant increases (p<0.05) in the in vitro antioxidant activities (FRAP, DPPH, ORAC) of brans/hulls, which positively correlated with TPC results (r = 0.72-0.88, r = 0.72-0.83, r = 0.59-0.83). Based on LC-MS/MS and fold change analyses, changes in the phenolic acid composition were predominant in fermented wheat bran. SSF of pea hulls generally led to changes in phenolic acid and kaempferol derivative contents. Additionally, fermented mustard bran was characterized with changes in the contents of phenolic acids, isorhamnetin derivatives and kaempferol derivatives. These results suggest that phenolics may be major contributors to the antioxidant capacity of fermented brans/hulls.  Findings from this study demonstrate SSF as a promising treatment to enhance the phenolic contents and antioxidant properties of brans/hulls. Further study into the impacts of SSF on the potential health attributes of these substrates is needed to transform them into value-added products.