An immobilized bifunctional xylanase on carbon-coated chitosan nanoparticles with a potential application in xylan-rich biomass bioconversion

Abstract

Immobilization technology offers many enzymatic advantages and overcomes the limitations of free enzymes. Bi- or multifunctional enzymes for industrial use have elicited much interest in recent years. The present work reported that a novel carbon nanoparticle-based supports was prepared by layer-by-layer self-assemble approach. The constructed bifunctional enzyme (ATXX) was successfully immobilized on the supports by covalent bonds. The prepared carbon-coated chitosan nanoparticles showed high binding capacity of about 289.9mgg−1-particles for ATXX. The Michaelis–Menten constants (Km) and maximal activity (Vmax) of immobilized ATXX were 4.83mgml−1 and 67.42μmolmin−1mg−1-particles (xylanase activity), as well as 6.13mgml−1 and 17.92μmolmin−1mg−1-particles (cellulase activity), respectively. The immobilized ATXX showed improved thermostability and storage stability compared with the free enzyme. The immobilized ATXX retained 82.6% xylanase activity after seven successive reactions. High-performance liquid chromatography (HPLC) analysis revealed that xylobiose (X2) was the main hydrolysis product released from beechwood xylan, birchwood xylan, and oat spelt xylan by immobilized ATXX. Wheat bran and wheat bran insoluble xylan could be directly hydrolyzed by immobilized ATXX, which demonstrated a potential use for xylan bioconversion to xylooligosaccharides by the immobilized ATXX.