Green ethanol production from cotton stalk

Abstract

This study was initiated to produce green ethanol from cotton stalk lignocelluloses using separate hydrolysis and fermentation (SHF) process. The influence of sodium hydroxide (2%) pretreatment at different residence times was also investigated. The effect of incubation period, enzyme concentration, pH and substrate concentration during enzymatic saccharification on sugar yield and ultimately on the ethanol production was studied. The results show that pretreatment with 2% NaOH for 90 min at 121°C was most effective and gave the highest percentage of cellulose (78.2±1.64%) along with highest delignification rate (63.9%). During the enzymatic saccharification, under the optimized conditions, maximum concentration of reducing sugars of the hydrolyzate was 67.83 ± 0.35 g/L with the maximum saccharification efficiency of 78.06%. The total sugars were 77.48 ± 2.37 g/L and total phenols were found to be 1.6 mm. Fermentation was carried out by using the enzymatically saccharified hydrolyzate and monoculture of Saccharomyces cerevisiae. Highest ethanol concentration of 22.93 ± 1.74 g/L with 0.36 g/g ethanol yield was achieved after 48 h of incubation at 30°C, pH 5 and 3% inoculum size.