Xylanase-polymer conjugates as new catalysts for xylooligosaccharides production from lignocellulose

Abstract

In the past few years, xylooligosaccharides produced from lignocellulosic biomass have attracted great attention. Enzyme catalysis is widely used because of its mild reaction conditions. In order to solve the shortcomings of poor stability and high cost of enzyme, a carrier-free enzyme immobilization technology was introduced. For this purpose, protein-polymer conjugates, kinds of carrier-free immobilized enzymes, were first established by growing poly (N-isopropylacrylamide) chains on xylanase using a grafting-from method, to obtain reusable and high-value xylanase. SDS-PAGE and circular dichroism spectra showed the successful preparation of xylanase-PNIPAAm conjugates, and the integrity of the protein secondary structure. The remaining activity of the xylanase-PNIPAAm conjugates after heat treatment (90 °C) for 60 min was approximately 20 % higher than that of the free xylanase, and a higher pH stability was obtained in the pH range of 2−8. The remaining activity of xylanase-PNIPAAm conjugates was more than 60 % after recycling 5 times. In addition, the mulberry bark synergistic treated by xylanase-PNIPAAm conjugates and cellulase was studied. More than 99.95 % yield of XOS in the degree of polymerization range of 1–3 was produced from mulberry bark. Overall, the construction of xylanase-PNIPAAm conjugates provides a novel method to produce xylooligosaccharides from waste biomass.