| Wheat bran, the main byproduct of wheat milling, contains approximately 30% of pentosans and 0.4%～0.7% of ferulic acid:which is esterified to some of the ararbinose resides of arabinoxylans. Thus, pentosan, xylooligosaccharide (XOs) and feruloyl oligosaccharides (FOs) could be prepared by different methods from wheat bran. XOs has been widely welcomed as a new functional food, and there is growing concern about the FOs because of its prominent bioactivity. The technology of release pentosans from the de-starched and de-proteinized wheat bran (NPNS bran) through alkali extraction, preparation of XOs from wheat pentosans by pentosanase and enzymatic preparation and purification of FOs from NPNS bran were investigated in this research. The main results were as follows:(1) The optimal technology for preparation of pentosans was extracted 1 part of wheat bran in 20 volume of 2.5% sodium hydroxide at 70℃for 2h, under this condition,17.31% of pentosans were released.(2) The optimal technology for praparation of XOs was hydrolyzed the pentosans solution (19.44mg/mL) by using 4g/L of enzyme at pH5.0,50℃for 6h, under this condition,4.98mg/mL of reducing sugars and 16.09 mg/mL of total soluble sugars were produced, the average degree of polymerization was 3.23.Decoloration technology:Five kinds of activated charcoals were used to decolor the xylooligosaccharide syrup and it was found that HC-303 showed best decoloration effect for XOs solution. The optimal decolorization technology was using 1.5g/L at 55℃for 75 min under constant strring. Under these conditions, the decoloration rate was up to 86.34%.De-salt technology:1mL of cation exchange resin 732 effectively adsorbde cations from 30mL of XOs solution, and 1mL of anion exchange resin 717 effectively adsorbed anions from 25mL of XOs solution. Regeneration of resin 732 was much easier than that of resin 717.After enzymic hydrolysis, decoloration and desalt, the oligosaccharide syrup containing 53.9% of oligosaccharide syrup which contained 12.4%,6.45% and 9.56% of xylobiose, xylotriose and xylotetraose respectively was abtained.(3) The optimal technology for preparation of FOs was to hydrolyze 1 part of NPNS wheat bran in 20 volume by using 3g/L of enzymes(a mixture of two parts of xylanase with one part of Viscozyme L in volume ratio) at pH4.5,60℃for 8h; under this condition 0.277g/g of soluble solids was produced, in witch 0.104g/g of reducing sugars,0.215g/g of total soluble sugars and 2.73mg/g of ferulic aicd in FOs were contained (calculate on the basisi of NPNS bran).FOs was seperated with Amberlite XAD-2 macroporous resin. The enzymic hydrolyzates which contained FOs (59.1μg/mL) or bound ferulic acid were uploaded to a column (10×300mm) (four volume of enzymic hydrolyzates to one volume of resin) at a flow rate of lmL/min to remove ferulic acid-free oligosaccharides, the resin was eluted with 50% of ethanol aqueous solution at 1mL/min to obtain FOs. The results showed that 91.04% of FOs was revovered.After enzymatic hydrolysis and purification,4.27% of FOs containing 3.77% of ferulic acid was abtained from wheat brain, and the composition of the FOs were mainly arabinose and xylose.
|
PDF Full Text Request