Enzymatic production of sugar from fungi and fungi-infected lignocellulosic biomass by a new cellulosomal enzyme harboring N-acetyl-beta-D-glucosaminidase activity

Abstract

Cellulosomes are scaffold proteins displaying enzymes on the cell wall to efficiently obtain nutrient sources. CcGlcNAcase is a novel cellulosomal component. Based on sequence analysis, CcGlcNAcase was predicted to be a chitinolytic enzyme based on high homology with the discoidin domain-containing protein and chitobiase/beta-hexosaminidase C terminal domain. CcGlcNAcase expression was notably increased when chitin was present. CcGlcNAcase produced N-acetyl-D-glucosamine from various lengths of N-acetyl-D-glucosamine. CcGlcNAcase bound to chitin (89%) and fungi (54.10%), whereas CcGlcNAcase exhibited a low binding ability to cellulose and xylan. CcGlcNAcase hydrolyzed fungi, yielding maximum 3.90 g/L N-acetyl-D-glucosamine. CcGlcNAcase enhanced cellulase toward fungi-infected lignocellulosic biomass, yielding 18 mg/L glucose (1.32-fold) and 1.72-fold increased total reducing sugar levels, whereas cellulase alone produced 13 mg/L glucose. Taken together, CcGlcNAcase can be utilized to enhance the degradation of fungi-infected lignocellulosic biomass and exhibits potential applications in the wood and sugar industry.