Synergistic degradation of cellulose by lytic polysaccharides monooxygenase HcLPMO and cellulase

Abstract:

[Objective] To study the synergistic degradation of cellulose by lytic polysaccharide monooxygenase HcLPMO and cellulase. [Methods] We used E. coli for heterologous expression of HcLPMO and studied the influences of various conditions on the activity detection of LPMOs with Amplex^TM Ultra Red as fluorogenic substrate. Subsequently, we studied the synergistic degradation of avicel and other biomass substrates with different proportion of HcLPMO and cellulase.[Results] We found the optimal filling liquid volume was 20% and the optimal induction temperature was 20℃ for HcLPMO expression. The results of activity determination show that HcLPMO had activity only when it was combined with copper ions. The optimal concentration of sodium ascorbate was 10^-4 mol/L. We also found that the concentration of Amplex^TM Ultra Red and horseradish peroxidase had little effect on the detection of enzyme activity. For the synergistic degradation of avicel by HcLPMO and cellulase, we found the optimal ratio of HcLPMO to cellulase was 2:3, and the yield of glucose increased by 99.48% compared with cellulase alone. In addition, for a variety of biomass substrates, HcLPMO and cellulase had better synergistic degradation efficiency on steam exploded straw and microcrystalline cellulose from which the yield of glucose increased by 63.81% and 59.43%, respectively, compared with using cellulase alone. For alkali treated corn cob and cassava residue, the yield of glucose only increased by 35.41% and 11.06%, respectively.[Conclusion] The appropriate ratio of HcLPMO and cellulase can effectively improve the efficiency of enzymatic degradation of cellulose, and substrate pretreatment is very helpful for the synergistic degradation of lignocellulose by HcLPMO and cellulase.