Optimization of Alkaline Organosolvent Pre-treatment of Sugarcane Bagasse for Bioethanol Production

Abstract

Industrial revolution and increasing population accelerated energy demand. Overdependencies on conventional fuels resulted in drastic environmental changes. Such challenges can be addressed by sustainable fuels. 2nd generation bioethanol produced by lignocellulosic biomass could be the best option in current scenario. But its complex structure is always challenging for its conversion to bioethanol. Pretreatment methods are requisite to deal with complex structure of lignocellulosic biomass. In this study sugarcane bagasse is pre-treated by the novel alkaline organosolvent pretreatment method. This study aims to optimize temperature (40-60), incubation time (1-3h), rpm (100-200), S/L ratio (15- 35) and concentration of NaOH (2-4%) to get maximum sugars at low cost. Optimization of the pretreatment was done by Box-Behnken design using Design Expert Software version 7 which gave 43 runs. The run 4 of the Box-Behnken design give the highest yield of the sugars i.e. 6.80g/l with optimized conditions as follows; concentration of alkali (4%), incubation time (2 hours), RPM (150), temperature (50 °C) and solid to liquid ratio (1:15). The ANOVA statistical analysis for the significant factor effecting the yield of the sugars was carried out. It was observed that only solid to liquid ratio significantly affect the yield of sugars from sugar cane bagasse. Clavispora lusitaniae yeast known to utilize xylose (5- carbon) sugars is used in this study for fermentation reaction. Yeast strain gave 83%, 58% and 32% ethanol yield with dilutions (5p, 10p) and pure acid hydrolysate respectively. Ethanol was not produced with alcoholic hydrolysate.