Production Of Enzymes From Aspergillus Niger By Liquid Culture And Their Application In Preparation Of Trans-ferulic Acid And Oligosaccharide

Mixed enzymes containing ferulic acid esterase and arabinoxylanase prepared from liquid culture of Aspergillus niger were used to hydrolyze destarched wheat bran to prepare trans-ferulic acid and oligosaccharide.1 Optimization of culture conditionsPlackett-Burman design and response surface methodology were used to optimize fermentation technology for production of mixed-enzymes (ferulic acid esterase and arabinoxylanase) by Aspergillus niger in conic flask. The results showed that mixed-enzymes production was influenced by 3 factors of the tested 8 factors according to Plackett-Burman design; Two response surface models and response surface plots were obtained by using response surface methodology to optimize 3 significant factors. The optimal fermentation condition were: pH 5.5 and 10% wheat bran, 0.28% NH4NO3, 0.2% KH2PO4, 0.08% MgSO4 ?7H2O, 0.31% NaNO3. The fermentation time and temperature were 4d and 32℃.2 Properties of ferulic acid esterase and arabinoxylanaseThe optimal pH of the mixed-enzymes reaction and stability were at 4.4 and 5.0, respectively, and the optimal temperature of the mixed-enzymes reaction and stabilitywere at 50 ℃ and 35℃, respectively. Furthermore, the metal ions ( Mn2+ Co2+ ) showed significant effect on the activity of arabinoxylanase.Inorganic ceramic membrane ultrafiltration with molecular weight cut-off of 20,000 and 100,000, respectively was also used to concentrate the enzymes, the results showed that the inorganic ceramic membrane with molecular weight cut-off of 20,000 could retain 80% mixed-enzymes when concentrated by 1.5 times.3 Other influencing parameters for enzymatic hydrolysisThe effective factors on the hydrolysis of de-starched wheat bran, including enzymatic hydrolysis time, the concentration of enzymes, the ratio of substrate to mixed-enzymes, the substrate particle size and pre-treatment of the substrate were investigated. Results showed that activity of ferulic acid esterase was inhibited by high concentration of ferulic acid. In the range of particle size between 2-0.149mm, the smaller the particle size was, the less the ferulic acid and oligosaccharides was released. The high pressure (0.1 MPa), microware treatments of de-starched wheat bran showed significant effect on the production of ferulic acid.4 Antioxidant activity of enzyme-released products from wheat branThe antioxidant activity of enzyme-released products from wheat bran was investigated their protection against peroxidation of linoleic acid. The results showed that the product had higher antioxidant activity than ferulic acid at the same concentration. Moreover, the enzyme-released products could effectively scavenge free radicals and protect against DNA damage caused by hydroxyl free radical in vitro.