Abstract
Sweet sorghum juice, a potential bioethanol feedstock, can be incorporated into the dry-grind ethanol process to improve sugar utilization efficiency, thereby enhancing ethanol yields. The juice is normally obtained by pressing the stalk through roller mills in tandem. Juice extraction by this process is known to be labor intensive, less efficient, and susceptible to considerable fermentable sugar loss due to microbial activities when stored at room temperature. Sweet sorghum juice extraction via diffusion has recently been proposed to improve sugar recovery efficiency. In this study, extraction kinetics based on the optimized diffusion parameters (8% grain loading, 85 °C, and 120 min) were determined to describe the mass transfer of sugars in sweet sorghum biomass during the diffusion process. Diffusion parameters obtained from previous studies were used to extract free sugars and convert them into ethanol using granular starch hydrolyzing enzymes (GSHE) and traditional enzymes. Ethanol yields at 72 h of fermentation mashes treated with GSHE and those with traditional enzymes were comparable (14.49–14.56%, v/v). Ethanol fermentation efficiencies also ranged from 88.92–92.02%.
Highlights
Sweet sorghum juice can be directly converted into bioethanol via anaerobic fermentation by yeastSaccharomyces cerevisiae [1,2,3,4]
Another study reported that co-fermenting corn starch with sweet sorghum juice resulted in a 37% reduction in the quantity of corn required in the dry-grind process [10]
A previous model study of fermentable sugar extraction and starch hydrolysis from sweet sorghum bagasse and grain flour via diffusion process showed the increase of sugar diffusivity from the sweet sorghum feedstock [17], but the mass transfer kinetics of the sugar molecules were not studied
Summary
Saccharomyces cerevisiae [1,2,3,4]. The fermentable sugars in the juice can be utilized as raw material for the industrial production of lactic acid by Lactobacillus sp. [5], acetone-butanol by Clostriduim acetobutylicum [6], and the production of other organic acids [7]. The integration of the sweet sorghum starch in the diffusion process via enzymatic hydrolysis could, as well, improve the overall fermentable sugar extraction from the energy crop. A previous model study of fermentable sugar extraction and starch hydrolysis from sweet sorghum bagasse and grain flour via diffusion process showed the increase of sugar diffusivity from the sweet sorghum feedstock [17], but the mass transfer kinetics of the sugar molecules were not studied. The optimized diffusion conditions obtained in the previous study were applied to extract sugars and hydrolyze starch from sweet sorghum feedstock. This was followed by a study of the ethanol fermentation performance using both traditional enzymes and granular starch hydrolysis enzymes (GSHE) Stargen 002. The utilization of GSHE in the ethanol process can eliminate the need for high temperature (>80 ◦ C) cooking during the starch hydrolysis and liquefaction stage reducing energy input [8,26,27]
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
