Abstract:

For reducing the cost of enzymatic preparation of xylo-oligosaccharides and improving the purity of the product, the conditions of induced expression of the recombinant xylanase and the parameters of enzymatic hydrolysis of xylan were studied. The effects of the inducer concentration, induction temperature, induction OD₆₀₀, and induction time on the recombinant xylanase production from recombinant Escherichia coli strain (pTrc99A-podoxyn11-DE3) were investigated. The enzyme dosage, enzyme hydrolysis time, and product distribution in the process of enzymatic hydrolysis were studied. The results showed that the optimal conditions were inducer concentration 5 mmol/L, the induction temperature 32℃, the induction time 8 h, and the induction OD₆₀₀ value 1.2. Under these conditions, the activity of recombinase could reach 5.72 U/mL. When the concentration of corn cob xylan was 20 g/L, temperature was 45℃, pH value was 5.5 and the amount of recombinant xylanase was 60 U/g, the hydrolysis rate was 49.90% and the yield of xylo-oligosaccharides was 21.75% after reacting for 12 hours. Under the condition of 20 g/L of poplar xylan, 45℃, pH value 5.5 and 35 U/g of recombinant xylanase for 14 hours, the rate of enzymatic hydrolysis was 79.50%, and the yield of xylo-oligosaccharides was 73.30%. Xylose was not detected in the hydrolysis products of two kinds of xylans by recombinant xylanase and the products were main xylobiose and xylotriose.

Key words: recombinant xylanase, inducted expression, xylo-oligosaccharide, senzymatic hydrolysis condition