Study On Enzymatic Preparation Of Feruloyl Oligosaccharides With Biological Activity From Wheat Bran

Many epidemiological studies have strongly suggested grain phenolic compounds play a crucial role in the prevention of chronic diseases. Ferulic acid, as a predominant phenolic acid in cereals, is esterified to some of the ararbinose resides of arabinoxylans of cereal cell walls. Wheat is a major crop and an important component of the human diet. Feruloyl oligosaccharides (FOs) are released from the arabinoxylans in wheat bran by mild acid hydrolysis or by treatment with a mixture of polysaccharide hydrolyzing enzymes. The prominent bioactivity of FOs may be important in preventing or reducing the progression of atherosclerosis by inhibiting the peroxidation of lipoproteins. So far, there is no report on FOs at home. In this work, the FOs were prepared from wheat bran insoluble dietary firber by treatment with xylanases from Bacillus subtilis, and their biological activity was mainly evaluated. Further, the theoretical parameters (O-H bond dissociation energy, Log P) of FOs were calculated by quantum chemistry, the structure-activity relationships were theoretically elucidated.The better resolution power for xylanases from B. subtilis was obtained by using the chosen analytical system with 100 mg/mL separating gel with 375 mmol/L pH 9.0 Tris/HCl buffer, and 50 mmol/L Tris/384 mmol/L glycine (pH 8.3) for the electrode-running buffer. Two endoxylanases were purified from B. subtilis xylanases by native polyacrylamide gel electrophoresis combined with homogenization extraction, designated xylⅠand xylⅡ. The specific activities were 193.2 U/mg protein for xylⅠand 472.1 U/mg protein for xylⅡ. The novel method for purification of endoxylanase is rapid, convenient and efficient,and makes bioactivity of the enzymes to be remained.Both of xylⅠand xylⅡhad similar optimum activities at pH 7.0 and at 50℃. Mn2+ ions enhanced their xylanolytic activities to 2.7-fold whereas Fe3+ completely inhibited them. The molecular weight of xylⅠand xylⅡwere estimated as 53.0 kDa and 98.8 kDa by SDS-PAGE, respectively. The Km and Vmax values with birchwood xylan as substrate were 1.11 mg/mL and 0.22 mgmL-1min-1 for xylⅠ, and 3.07 mg/mL and 0.57 mgmL-1min-1 for xylⅡ.Insoluble dietary fiber with 40% of yield was prepared from wheat bran by treatment withα-amylase, protease and amyloglucosidase. The content of arabinoxylans is ca 54.7% of wheat bran insoluble dietary fiber with 0.90% ferulic acid. The wheat bran insoluble dietary fibre was hydrolyzed by xylanases from B.