Improvement of GH10 xylanase activity based on channel hindrance elimination strategy for better synergistic cellulase to enhance green bio-energy production

Xylanase is widely used for the degradation lignocellulosic biomass as an important accessory enzyme. But productive hydrolysis of the recalcitrant lignocellulose also requires for applicable pretreatment with environmental friendliness. Meanwhile, the complicated industrial processes also demand for catalytically efficient enzymes with more resistance to both pH and heating conditions, which barely exist for the wild types. In this study, the dominant mutant H51K/Q118A from Gloeophyllum trabeum derived GtXyn10 (WT) was obtained by directed evolution. Compared to the WT, apart from the impressive pH resistance from pH 1.0–9.0, the dominant mutant H51K/Q118A also exhibited higher specific activity (2.5-fold; 2510 vs. 1010 U/mg), higher catalytic efficiency (2.4-fold; 460 vs. 190 mL/s‧mg), and better thermostability (with t1/2 at 80 °C extend by 10 min). When ‘Seawater + Feton’ pretreatment was applied, the lignin clearance rate reached 62.5%, 86.6% higher than that of feton pretreatment (33.5%). After pretreatment of ‘Seawater + Feton’, Compared with the cellulase-only treatment (159 μmol/g), synergistic hydrolysis with both H51K/Q118A and cellulase (236 μmol/g) increased the fermentable sugar yields from bagasse by 48.4%. In combination with the optimized pretreatment and synergistic hydrolysis of the modified xylanase and cellulase, the fermentable sugar production for green bio-energy was realized with efficiency.