Enhancing hydrolysis of lignocellulosic biomass through molecular modification of lytic polysaccharide monooxygenase from Aspergillus niger

Lytic polysaccharide monooxygenase (LPMO) of Auxiliary Activity 9 family has great potential for lignocellulose biomass degradation, and obtaining AA9 LPMOs with high catalytic activity and thermalstability is necessary for its industrial application. In this study, rational design and molecular modification was conducted on AnLPMO15g from Aspergillus niger to boost its performance on lignocellulose hydrolysis. The catalytic performance of mutant AnLPMO15g-293 (C293F) and AnLPMO15g-351 (S351F) with increased α-helix content in the secondary structure were improved. The catalytic efficiency (K_cat/K_m) of C293F and S351F on 2,6-dimethoxyphenol was 1.27 and 1.17 times higher than that of AnLPMO15g respectively, and their activities on Avicel® increased by 81.17% and 40.78%, respectively. The half-life of C293F and S351F at 55 ℃ was 1.5 and 2.5 times longer than that of AnLPMO15g. Surface plasmon resonance analysis showed that the association velocity constant (Ka) of S351F increased tenfold compared with that of AnLPMO15g, indicating the substrate affinity of S351F was significantly improved. When C293F and S351F acted together with cellulase on straw powder, the reducing sugar yields increased by 1.81 and 1.53 times and the synergistic degree increased 30.7% and 11.8%, respectively. This study provides a good alternative for preparing efficient enzyme cocktails to hydrolyze lignocellulosic biomass.