Examining Committee 
Dr. Loong-Tak, Chair 
Dr. Gisele LaPointe, Advisor 
Dr. Iris Joye, Co-Advisor  
Dr. Keith Warriner, Department Member 

TITLE: Enzymatic preparation and in vitro fermentation of wheat bran hydrolysates 

ABSTRACT:  Arabinoxylan-oligosaccharides (AXOS) are water-soluble oligosaccharides that originate from arabinoxylan (AX) by enzymatic hydrolysis and have potential as prebiotics. The objective of this project is to prepare water-soluble hydrolysates from wheat bran (WB), an AX-rich cereal material, through the treatment of endo-1,4-β-xylanase from Neocallimastix patriciarum, and investigate the fermentability of WB hydrolysates in a batch in vitro environment up to 72 hours with mixed human gut microbiota from fresh human fecal samples collected from three healthy adult donors. The result suggests that water-soluble hydrolysates were successfully produced from enzymatic hydrolysis of WB after removing the starch and protein. The Size-Exclusion High-Performance Liquid Chromatography (SEC-HPLC) analysis shows that WB hydrolysates contain oligosaccharides and monosaccharides with a molecular weight of less than 1 kDa. The WB hydrolysates are rapidly fermented by the mixed human gut microbiota, as evidenced by increasing the optical density of the mixture and lowering the pH after 6 hours of fermentation. The qPCR results indicate that the fermentation of WB hydrolysates promotes Bifidobacterium growth irrespective of the initial Bifidobacterium load of the donor. The 16S rRNA gene sequencing analysis shows that the in vitro fermentation of WB hydrolysates increases the relative abundance Proteobacteria and lowers the relative abundance of Bacteroidetes, which indicates WB hydrolysates are less selective to the beneficial bacteria compared to conventional prebiotics. The prebiotic effect of oligosaccharides adds value to WB as a food ingredient as consumers demand healthier food, and the benefits of prebiotics are well established.