Studies on effect of alkali pretreatment of banana pseudostem for fermentable sugar production for biobutanol production

Abstract

Aim: In this study, effectiveness of alkali pretreatment of banana pseudostem for the production of biobutanol by fermentation using Clostridium sporogenes under strict anaerobic conditions was studied. Methodology: Banana pseudostem was pretreated by alkali soaking at constant temperature (30, 50 and 70°C) and concentration of 0.25 to 2% (w/v) at solid to liquid ratio of 1:10 for 24 hr to depolymerize the lignocellulosic biomass. Further to increase delignification, the alkali soaked samples were subjected to thermal treatment at 121°C for 15 min. The hydrolysates were subjected to acetone-butanol-ethanol fermentation using Clostridium sporogenes to produce butanol. Results: Maximum delignification of 92% was obtained at 30°C soaking temperature with 2% NaOH (w/v). Increase in temperature led to increase in delignification but also resulted in reduced recovery of cellulose. Maximum glucose yield of 524 mg g-1glucan was obtained from the pretreated biomass. Fermentation of hydrolysate obtained from alkali soaking pretreatment by C. sporogenes under anaerobic condition resulted e c in 10.12 g l-1of butanol with a yield of 0.326 g g-1of total sugar consumed and it was much higher compared to untreated biomass. Interpretation: Alkali soaking pretreatment at 30°C and alkali concentration of 1.5% (w/v) was effective to depolymerize the biomass to obtain maximum sugar and butanol yield from banana pseudostem. Thermal treatment was not effective in increasing the production of butanol due to pseudo lignin formation and presence of inhibitors.