Characterization of the recombinant GH10 xylanase from Trichoderma orientalis EU7-22 and its synergistic hydrolysis of bamboo hemicellulose with α-glucuronidase and α-L-arabinofuranosidase

Abstract

Here the recombinant GH10 xylanase (HoXyn10) was investigated for biochemical characteristics and synergistic effect with α-glucuronidase (AnGus67) and α-L-arabinofuranosidase (AnAxh62A) on extracted Maso bamboo hemicellulose (BCH) to produce xylooligosaccharides (XOS). The GH10 endo-β-1, 4-xylanase from Trichoderma orientalis EU7–22 is heterologously expressed in Pichia pastoris GS115. The crude HoXyn10 showed three bands on the SDS-PAGE profile and one of the proteins was N-glycosylated. The optimum pH and temperature of HoXyn10 were pH= 6.0 and 65 °C, respectively. It showed a wide range of pH stability and remained more than 80% of optimal activity at pH4.5–8.0 after holding at 40 °C for 60 min. HoXyn10 was highly stable at 50 °C without substrate and the residue xylanase activities were retained 97% and 83% after incubating for 2 h and 18 h, respectively. HoXyn10 displayed high activities and almost the same catalytic efficiency to oat-spelt xylan (OSX), Beechwood xylan (BWX) and wheat arabinoxylan (WAX). Notably, the HoXyn10 exhibited apparent activity on Avicel, but showed no activity on CMC-Na. The hydrolytic products from oligosaccharides (X3-X6) by HoXyn10 were all xylose (X1) and xylobiose (X2). The results from FT-IR and NMR showed the backbone of extracted BCH was (1→4)-linked β-D-xylopyranose and the main side chains were α-L-arabinofuranose residues and 4-O-methyl-D-glucuronic acid residues. Based on the characterized structure, when BCH was synergistically hydrolyzed with HoXyn10, AnGus67 and AnAxh62A using appropriate strategy, the yield of xylooligosaccharide (XOS) and xylose were 50.3% and 14.7%. The results indicated HoXyn10 might be a promising tool for various hemicellulose hydrolysis and Maso bamboo hemicellulose is a promising source for XOS production.