Objectives: Efficient enzymatic saccharification of plant cell wall material is key to industrial processing of agricultural and forestry waste such as straw and wood chips into fuels and chemicals.
Results: Saccharification assays were performed on steam-pretreated wheat straw under ambient and O2-deprived environments and in the absence and presence of a lytic polysaccharide monooxygenase (LPMO) and catalase. A kinetic model was used to calculate catalytic rate and first-order inactivation rate constants of the cellulases from reaction progress curves. The addition of a LPMO significantly (P < 0.01, Student's T test) enhanced the rate of glucose release from 2.8 to 6.9 h(-1) under ambient O2 conditions. However, this also significantly (P < 0.01, Student's T test) increased the rate of inactivation of the enzyme mixture, thereby reducing the performance half-life from 65 to 35 h. Decreasing O2 levels or, strikingly, the addition of catalase significantly reduced (P < 0.01, Student's T test) enzyme inactivation and, as a consequence, higher efficiency of the cellulolytic enzyme cocktail was achieved.
Conclusion: Oxidative inactivation of commercial cellulase mixtures is a significant factor influencing the overall saccharification efficiency and the addition of catalase can be used to protect these mixtures from inactivation.
Keywords: Catalase; Cellulase; Fenton chemistry; Kinetic modelling; Lytic polysaccharide monooxygenase; Pretreated wheat straw; Reactive oxygen species.