Location: Bioenergy ResearchTitle: Challenges of cellulosic ethanol production from xylose-extracted corncob residues Author
Submitted to: BioResources
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/6/2011
Publication Date: 9/8/2011
Citation: Zhang, L., Li, J., Li, S., Liu, Z. 2011. Challenges of cellulosic ethanol production from xylose-extracted corncob residues. BioResources. 6(4):4302-4316. Interpretive Summary: Starch-to-ethanol is a classic means for production of fuel ethanol. However, the use of starch for ethanol production competes for grain supplies and food security for humans and animals worldwide. Emerging interest in ethanol production using cellulosic biomass such as agricultural crop residues is a promising technology for the second generation production of biofuels. Combined xylose production using corncobs and subsequent ethanol production using the xylose-extracted corncob residue (X-ER) is a new concept for production of value-added renewable products. This research represents the first characterization of the X-ER and evaluation of its potential use for cellulosic ethanol production. We found that cellulose-rich X-ER has a potential as a substrate for cellulosic ethanol production. However, the X-ER produced by the current industrial xylose-production process is not readily convertable to ethanol and further pretreatment is needed to enhance its conversion. Findings of our research will aid further investigation and decision-making toward improved and integrated bioprocessing procedures using corncobs and its byproduct X-ER for lower-cost production of a value-added product and cellulosic ethanol.
Technical Abstract: Xylose production using corncobs is an established industrial practice. The cellulose-rich xylose-extracted corncob residue (X-ER), as a byproduct, is a potential energy resource. Efforts to convert the cellulose fraction of X-ER to ethanol have been unsatisfactory due to a lack of understanding of the substrate characteristics. The present study characterized X-ER for its potential utilization in conjunction with the sequential production of xylose and cellulosic ethanol. We found the current dilute acid treatment procedures used for the corncobs by the xylose-production industry were insufficient for deconstruction of corncob cellulose structure in order to release available sugars for the subsequent cellulosic ethanol conversion. After a secondary dilute acid hydrolysis of the X-ER, an additional 30% hemicellulose was recovered. In addition, a more efficient enzymatic hydrolysis of X-ER was observed resulting in a significantly higher yield of glucose conversion compared with an untreated X-ER control. These results suggest X-ER can be utilized for cellulosic ethanol production; however, the current industry processed X-ER is not ready for immediate applications of economic ethanol conversion. Based on the results of the current research, it is possible to pursue a combined production of xylose and cellulosic ethanol from corncobs and its byproduct X-ER using improved corncob pretreatment procedures and fermentation strategies.