Improving lignocellulose degradation using xylanase-cellulase fusion protein with a glycine-serine linker

The fungal hydrolytic system efficiently degrades lignocellulosics efficiently. We previously characterized two hydrolytic enzymes from Gloeophyllum trabeum, namely, endoglucanase (Cel5B) and xylanase (Xyl10g). To enhance lignocellulosic degradation, we designed a fusion protein (Xyl10g GS Cel5B) using a glycine-serine (GS) linker and expressed it in Pichia pastoris GS115, which produced a hydrolytic fusion enzyme for the degradation of lignocellulosics. Purified Xyl10g GS Cel5B protein has a molecular weight of approximately 97 kDa and shows a lower specific activity than Xyl10g or Cel5B. However, Xyl10g GS Cel5B can degrade popping-pretreated rice straw, corn stover, kenaf, and oak more efficiently than the mixture of Xyl10g and Cel5B, by about 1.41-, 1.37-, 1.32-, and 1.40-fold, respectively. Our results suggest that Xyl10g GS Cel5B is an efficient hydrolytic enzyme and a suitable candidate for degrading lignocellulosics to produce fermentable sugar.