Studies on delignification and inhibitory enzyme kinetics of alkaline peroxide pre-treated pine and deodar saw dust

Abstract

Delignification of lignocellulosic biomass by alkaline peroxide pre-treatment is a preliminary important step for an overall biomass fractionation process. In the present work, saw dusts are pre-treated by aqueous alkaline peroxide solution under different temperatures over a predetermined time. It is seen that Combined Pre-treatment (CP) removes a substantially higher quantity of lignin from biomass under a particular temperature. At elevated temperatures, the extent of delignification is observed much better. The % removal is: [PR: 19.35%(30 °C):25.26%(50 °C):33.30%(100 °C)]; [CD:14.64%(30 °C):23.64%(50 °C): 28.83%(100 °C)]. Batch kinetics is investigated with certain models and corresponding parameters are estimated. As pre-treatment severity is strongly correlated to the pre-treatment temperature, increased value of “potential degree of delignification” is observed at escalated temperatures. Kinetics of enzymatic hydrolysis of delignified biomass shows decreased product inhibition with increased substrate concentration under a particular enzyme loading. Starting with a combination of 50 g/L substrate concentration with an enzyme loading of 13.23 g/L, an optimum concentration of 17.2 g/L and 21.19 g/L of glucose are produced from Pinus roxburghii and Cedrus deodara respectively. Experimental data fit quite well with the competitive inhibition kinetics based theoretical models with r2 ≥0.95. It is inferred that enzymes are competitively inhibited by glucose.