Chemical composition analysis of various genetically modified sorghum traits: Pretreatment process optimization and bioethanol production from hemicellulosic hydrolyzates without detoxification

Abstract

Compared to other inedible agricultural based feedstocks such as corn stover, rice husk, wheat straw and sugarcane bagasse, sorghum biomass (stalks and leaves) possess elevated credentials towards biofuel production which is highly tolerant against heat and drought conditions. Therefore, a novel sorghum phenotype was generated through genetic mutations called “brown midrib” which possesses low lignin content with enriched palatability. In the present study, the chemical composition of fourteen genetically modified sorghum biomass traits were analyzed which constitute, 52.7–60% of structural carbohydrates (cellulose and hemicellulose) and 11.6–17.7% of lignin. Due to the presence of low lignin content, pretreatment was performed using low energy input system to achieve maximum hemicellulose hydrolysis with minimized levels of sugar decomposition products. As a result, 88–92% of hemicellulose hydrolysis was attained with low amount of furfural (0.34–0.49 g/L) and 5-Hydroxymethylfurfural (0.38–0.56 g/L). Furthermore, fermentation was also performed without detoxification of pretreatment derived hemicellulosic hydrolyzate to evaluate the effect of fermentative inhibitors on ethanol-producing yeast. As a result, 88.8–92.5% ethanol conversion efficiency and 0.45–0.47 (gp/gs) ethanol yield were achieved within 15 h of fermentation time period.