Ozonolysis Pretreatment of Wheat Straw for Enhanced Delignification: Applying RSM Technique for Modeling and Optimizing Process

Wheat straw is widely used for animal feed and biorefinery to sugar production. However, cellulose, which is the major source of sugar, is protected by lignin. Ozone is a powerful oxidizer that can deconstruct lignin and makes cellulose accessible to enzymatic digestion. The aim of this study is the delignification of wheat straw using ozonolysis technology as a green, environmentally friendly, and energy-efficient process. Modeling and optimization were performed by response surface methodology and the effects of five factors including ozone production rate (1, 2, and 3 g/h), reaction time (15, 30, and 45 min), the flow rate of ozone/oxygen (0, 3, and 6 L/min), moisture content (100, 200, and 300% w/w) and urea (0, 1.5, and 3% w/w) were investigated. The results of this study showed that the highest delignification (50%) was observed in the highest levels of ozone amount, time, flow rate, urea, and the lowest level of moisture content. The flow rate and moisture content factors were the most contributing factors in the delignification process with 36 and 20%, respectively. Under optimal conditions, 49.8% of delignification was obtained at an ozone amount (3 g/h), time (45 min), flow rate (5.7 L/min), moisture content (100% w/w), and urea amount (3% w/w) with a desirability index of 0.99. The response surface method creates a desirable fitness between the experimental and predicted responses with R2=0.90. The results showed that the ozonolysis process using the proposed factors can be used to delignification of wheat straw.