Hydrolytic boosting of lignocellulosic biomass by a fungal lytic polysaccharide monooxygenase, AnLPMO15g from Aspergillus niger

Lytic polysaccharide monooxygenases (LPMOs) is a group of copper-dependent oxygenases that can cleave polysaccharides. Especially, the fungal LPMOs of Auxiliary Activity 9 (AA9) family can degrade cellulose to boost the lignocellulosic hydrolysis. LPMOs in Aspergillus niger, an important industrial producer of glycoside hydrolases, have not been studied. In this work, AnLPMO15g from A. niger was first cloned and expressed, and proved to be able to act on Avicel (R), straw, Carboxyl Methyl Cellulose (CMC) and xylan. MALDI-TOF/TOF mass spectrometry analysis indicated that it oxidatively cleaved the glycosidic bonds at Cl position. AnLPMO15g could obviously promote the catalytic efficiency of cellulase when acting on Avicel (R) and lignocellulose. The reducing sugar yield of Avicel (R) and straw catalyzed by AnLPMO15g together with cellulase were 1.93 and 2.31 times of those by cellulase only. The corresponding synergism degrees were 1.18 and 1.27 respectively. The increase in reducing sugar yield when AnLPMO15g acted together with xylanase on xylan was proved to be addition rather than synergism of these two enzymes. In conclusion, AnLPMO15g could be beneficial for plant cell wall decomposition and was a promising candidate to boost the efficiency of enzyme cocktails for lignocellulose degradation.