Synergistic Activity of Auxiliary Activity 9 from Chaetomium globosum on Hydrolysis of Xylan by Xylanase

As an effective strategy to promote the enzymatic saccharification of lignocellulose, there has been much attention to synergistic proteins for cellulose hydrolysis. Such synergistic proteins are capable of provide synergism to the enzymatic hydrolysis of cellulose. Auxiliary activity family 9 (AA9) is a fungal class of lytic polysaccharide monooxygenases (LPMOs) and known to have synergism on cellulose degradation by performing an oxidative cleavage of the substrate. Previously, an AA9 identified from Chaetomium globosum (CgAA9) was expressed in Escherichia coli, and showed a synergism on cellulose hydrolysis. In this study, we showed a synergistic activity of the CgAA9 in xylan hydrolysis for the first time. The expression of mRNA for CgAA9 was induced when C. globosum was grown on xylan. The recombinant CgAA9 showed a synergism (1.3 fold) on the hydrolysis of beechwood xylan by xylanase in the presence of sodium azide, which was added as a reducing cofactor for CgAA9. The synergism of CgAA9 on xylan hydrolysis shown in this study provides an insight into a broader spectrum of substrates for AA9s, and will be applicable for more efficient saccharification of lignocellulose containing xylan in addition to cellulose.