Water-soluble sugars of pedigreed sorghum mutant stalks and their recovery after pretreatment

Authors: XU, YOUJIE - Kansas State University; LI, JUN - Kansas State University; Xin, Zhanguo; Bean, Scott; Tilley, Michael - Mike; WANG, DONGHAI - Kansas State University

Submitted to: Applied Sciences
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/5/2020
Publication Date: 8/7/2020
Citation: Xu, Y., Li, J., Xin, Z., Bean, S.R., Tilley, M., Wang, D. 2020. Water-soluble sugars of pedigreed sorghum mutant stalks and their recovery after pretreatment. Applied Sciences. 10(16):5472. https://doi.org/10.3390/app10165472.
DOI: https://doi.org/10.3390/app10165472

Interpretive Summary: Water-soluble sugars may contribute to a significant amount of biomass from sorghum stalks. However, their relative contribution to the total biomass in different lines is not clear. This manuscript analyzed 16 representative sorghum mutant stalks for the content of soluble soluble sugars, cellulose, and liginin. In some mutant lines, soluble sugars can contribute to more than 40% of the total biomass weight. Our results suggest that a pre-washing step is beneficial to recover the water-soluble sugars before subjecting to the pretreatment process in order to avoid sugar losses or degradation during the pretreatment stage. This finding can enhance the production efficiency of bioenergy feedstocks.

Technical Abstract: The chemical composition of biomass, especially the carbohydrate content, is a critical indicator of a biomass source’s potential for biofuel application. This study characterized the properties of 16 representative pedigreed sorghum mutant stalks with various water extractive contents. The objectives of this study were to evaluate the recovery of sucrose and its hydrolysis products–glucose and fructose–during the dilute sulfuric acid pretreatment process at conditions typically used to pretreat lignocellulosic biomass, and to determine the relationship between water extractive contents and sugar recovery after pretreatment. Dilute acid pretreated sorghum stalks demonstrated good enzymatic digestibility of greater than 82.4% glucose yield for all the treated samples with more than 82.3% cellulose recovery and 85% hemicellulose removal. A single-step, one-pot process was recommended for sorghum mutant stalks with less water-extractive content (<40%, w/w) to reduce processing cost and minimize wastewater disposal since the majority of sugars will be recovered after dilute acid pretreatment with a minimal amount of degradation products. However, for sorghum mutant stalks with high water-extractive content (>40%, w/w), a pre-washing step is beneficial to recover the present water-soluble sugars before subjecting to the pretreatment process in order to avoid sugar losses or degradation during the pretreatment stage. Thus, different processing technology should be applied to lignocellulosic biomass with various water-extractive contents and water-soluble sugar concentrations.