The influence of photosynthetic pigment chlorophyllin in light-driven LPMO system on the hydrolytic action of cellulases.

It has been demonstrated that LPMO reactions can be driven by light, using the photosynthetic pigment chlorophyllin to achieve efficient oxidative degradation of cellulose. However, the effect of chlorophyllin on cellulases remains unclear. This study discovered that chlorophyllin does not affect the hydrolytic activity of cellulases under dark conditions. However, under light exposure, chlorophyllin-derived reactive oxygen species (ROS) exhibit a strong inhibitory effect on cellulases. These ROS primarily inhibit the hydrolytic action of endoglucanase II (Cel5A) and cellobiohydrolase II (Cel6A), while the action of cellobiohydrolase I and β-glucosidase remains unaffected. Scavenger studies revealed that singlet oxygen (O₂) is the key inhibitory ROS responsible for the inhibition of Cel5A and Cel6A. The removal of O₂ by sodium azide effectively mitigates this inhibition, increasing the conversion yield of cellulose to glucose by 25.9 % when using the light-driven LPMO system in conjunction with cellulases. This study provides new insights into the role of chlorophyllin-derived O₂ in hindering hydrolytic action of cellulases and demonstrates the successful mitigation of this inhibition by sodium azide, thereby enhancing the cooperative degradation of cellulose to glucose by the light-driven LPMO system and cellulases.