Exploring the use of supercritical carbon dioxide in enzymatic hydrolysis of cellulosic substrate

Abstract

Enzymes are critical components for production of fermentable sugars in lignocellulosic biorefineries. Their activity could be influenced by various reaction parameters. Herein, a formulated cellulolytic enzyme cocktail was immobilized into mesoporous aerogel material and used under high pressure environment of supercritical CO2 (scCO2). The cocktail was immobilized at different enzyme loads (36.0 to 144.0 mg enzyme/g aerogel) using sol-gel entrapment method and scCO2 drying. The immobilized cocktail at 144.0 mg/g aerogel enzyme load retained a residual yield of >50.0 % after fourth cycle of reuse compared to first cycle under atmospheric pressure. Sugar yield by the cocktail aerogel was below 10 wt% in second cycle under scCO2 due to enzyme leaching. Additionally, surface area and porous volume of reused aerogels was decreased over the reuse cycles. The study suggests that scCO2 could be employed for aerogel preparation after optimizing the immobilization process for pure enzymes rather than crude enzymes.