Study On Enzymatic Hydrolysis Of Brewer’s Grains For The Preparation Of Feed Containing Xylooligosaccharides

Xylooligosaccharide is a new kind of green feed additive,which can improve the animal intestinal micro-ecological environment,enhance immunity and improve the utilization ratio of feed.Brewer’s grains is a by-product of beer industry which is rich in protein,carbohydrate,fat,mineral elements and other nutrients,but also contain cellulose and hemicellulose and other anti-nutritional factors.The application of brewer’s grains in animal feed is limited.Based on the analysis of the HPLC-ELSD content of xylooligosaccharides,.the pretreatment and enzymatic hydrolysis conditions for the preparation of xylooligosaccharides from brewer’s grains and the preliminary application was made in the feeding process of weaned piglets and fattening pigs were discussed in this paper.The main results were as follows:1.Establishment of HPLC-ELSD method for determination of xylooligosaccharides in brewer’s grainsChromatographic column was COSMOSIL Sugar-D(250mm×4.6mm,5μm),mobile phase: acetonitrile: water(69:31,V/V),the flow rate:0.9mL/min,column temperature:40℃,injection volume: 3μL,evaporator temperature: 78℃,flow rate of carrier gas:1.6L/min,carrier gas pressure:0.5MPa.The results showed that the calibration curve was linear over the content of Xylobiose-Xylopentaose in the range of 0.024mg/m L-0.245mg/mL,the detection limits were 0.025mg/mL,0.025mg/mL,0.024mg/mL,0.024mg/mL,the limits of quantification were 0.091mg/mL,0.091mg/mL,0.089mg/mL,0.889mg/mL,The retention time of RSD were 0.203%,0.224%,0.233% and 0.252%,and the spiked recoveries rate were 97.31-99.83%.2.Studies and optimization of pretreatment process of brewer’s grainsEffects of xylooligosaccharides production on the pretreatment methods(ultrasonic,microwave,high temperature cooking method and chemical pretreatment)and pretreatmen process(sodium carbonate concentration,hydrogen peroxide concentration,solid-liquid ratio,pretreatment temperature,pretreatment time)were studied by using single factor experiments with brewer’s grains as raw material.On the basis of previous results,the most significant factors were optimized by using orthogonal experiment.The results showed that the optimizal pretreatment conditions were,sodium carbonate content 0.7%,hydrogen peroxide content 0.1%,solid-liquid ratio 1:5,pretreatment temperature 115℃,pretreatment time 30 min.Under these conditions,the yield of xylooligosaccharide was 19.4693mg/g.3.Studies and optimization of enzymatic hydrolysis conditionsEffects of enzymolysis conditions such as initial pH value,xylanase content,cellulase content,hydrolysis temperature and hydrolysis time were studied on the yield of xylooligosaccharides by using single-factor experiments.Based on the results of single-factor experiments,the enzymolysis conditions were optimized by using response surface test.The quadratic regression equation model of initial pH value,xylanase,cellulase,enzymatic hydrolysis temperature and hydrolysis time on the yield of xylooligosaccharides was established.The results proved to be highly reliable,which R-squared of the model was 0.9433,means that 94.33% of xylooligosaccharides production can use this model to explain,C.V is 3.33% and SNR is 17.318.The yield of xylooligosaccharide reached 23.867mg/g under the optimal conditions of enzymatic hydrolysis(initial pH 5.5,xylanase 201U/g,cellulase 248U/g,hydrolysis temperature of 48℃,hydrolysis time 3h),compared with the theoretical predictione of 23.765mg/g,the relative error is only 0.43%,which showed that the model can predict the actual situation of the production of xylooligosaccharides in this conditions.