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

• Published in: Journal of environmental chemical engineering Vol. 6; no. 4; pp. 5625 - 5634
• Main Authors: Deshavath, Narendra Naik, Mahanta, Sushmita, Goud, Vaibhav V., Dasu, Veeranki Venkata, P., Srinivasa Rao
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01-08-2018
• Subjects: Ethanol; Fermentative inhibitors; Hemicellulose hydrolysis; Mutant sorghum traits; Pretreatment; Mutant sorghum traits; Pretreatment; Ethanol; Hemicellulose hydrolysis; Fermentative inhibitors
• ISSN: 2213-3437; 2213-3437
• DOI: 10.1016/j.jece.2018.08.002

•Due to the presence of low lignin content, pretreatment conducted in low energy input system.•Pretreatment process was optimized based on the maximum pentose sugars yield and low amount of furfural.•Around 88–92% of hemicellulose hydrolysis was attained at 121 °C, 0.2 M H2SO4 and 120 min.•Because of lower amounts of inhibitors, fermentation performed without detoxification of pre-hydrolyzate.•A significant ethanol conversion efficiency (88.8–92.5%) was achieved by using Pichia stipitis.
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.