Study On Enzymatic Preparation Of Feruloyl Oligosaccharides

Brewer's spent grain is the main by-products in beer production,which is accounting for about 85%of all by-products.Brewer's spent grain is a solid substance left after the malt of the beer production material is gelatinized,saccharified,and filtered.Brewer's spent grain is rich in cellulose and hemicellulose,The production is huge.Feruloyl oligosaccharides?FOs?is the functional oligosaccharides which link with ferulic acid and oligosaccharides by ester bonds.FOs has the physiological functions of ferulic acid and oligosaccharides,which is mainly from plants cell wall.Therefore,brewer's spent grain can become an important source of FOs,increasing the added value of brewer's spent garin and reducing environmental pressure.?1?Ferulic acid esterase is a kind of carboxylesterase,which hydrolyzes the ester bond between ferulic acid and oligosaccharides to release ferulic acid.For the cellulase industrial production strain containing ferulic acid esterase,Penicillium oxalicum 114-2 was knocked out by the Agrobacterium-mediated homologous recombination to obtain the correct knockout transformant.Three commercial enzymes which don't contain ferulic acid esterase?cellulase 1;cellulase 2;xylanase?were used to hydrolyze the brewer's spent grain to prepare FOs.On the basis of single factor,three kinds of commercial enzymes were subjected to the response surface method.The best compounded result was that cellulase 1 was 154.62 U·g^-1 substrate,cellulase2 was 114.18 U·g^-11 substrate,and xylanase was 143.94 U·g^-1 substrate.The optimal enzymatic hydrolysis conditions were studied on the results of optimal enzyme addition.The results was:substrate concentration 15 g·L^-1,pH 6.0,enzymatic hydrolysis time 10 h,enzymatic hydrolysis temperature 40?.Under the condition,the yield of FOs was 8.06?mol·g^-11 substrate.?2?The FOs hydrolysate was first precipitated by ethanol to determine the optimum ethanol precipitation concentration of 90%.Further,it was separated by macroporous adsorption resin D101 to obtain a solid sample of FOs.The FOs solid sample contains 3.06%(w·w^-1)of bound ferulic acid,and its monosaccharide composition is mainly xylose and arabinose.The FOs solid sample was analyzed by ultraviolet spectroscopy and infrared spectroscopy to prove the presence of esterified ferulic acid and ester-containing saccharide.?3?FOs has good in vitro antioxidant capacity.Experiments showed that FOs had good scavenging effects on hydroxyl radicals,DPPH free radicals and superoxide anion radicals.FOs also had strong reducing power and chelation with metal ions.The antioxidant activity of FOs was higher than ferulic acid and xylooligosaccharides.Both FOs and xylooligosaccharides promote the growth of Pediococcus acidilactici and Bifidobacteria.Through antibacterial experiments on Escherichia coli and Staphylococcus aureus,FOs did not inhibit Escherichia coli and Staphylococcus aureus,but promoted their growth.