Efficient saccharification of cellulose by a photo-assisted biocatalysis system

Lytic polysaccharide monooxygenases (LPMOs) from auxiliary activity family 9 (AA9) oxidize crystalline cellulose and contribute to cellulose saccharification by cellulase. However, the catalytic efficiency of LPMO is low, which makes the whole process of cellulose saccharification time-consuming. In this study, a photo-assisted biocatalysis system was developed to improve the efficiency of cellulose saccharification. The double mutant of MtC1LPMO (R17L/N25G) was firstly constructed, which resulted in a nearly one-fold increase in enzymatic activity. Molecular dynamics simulations were applied to explore the molecular mechanism of the enhanced activity of R17L/N25G. A novel biocatalysis system consisting of R17L/N25G and photocatalyst TiO2/BiOBr/g-C3N4 (TGB) was established, which resulted in a 16-fold increase in catalytic efficiency and a 26.9% increase in productivity. In addition, the results of cellulose conversion at high solids loading (18%) showed benefits under industrially relevant conditions. The mechanism underlying a more efficient cellulose saccharification process using this system was proposed. The significant enhancement of cellulose saccharification efficiency indicates that the photo-assisted biocatalysis system may have broad industrial applications.