Pretreatment of Corn Stover by Soaking in Aqueous Ammonia

Abstract

Soaking in aqueous ammonia (SAA) was investigated as a pretreatment method for corn stover. In this method, the feedstock was soaked in aqueous ammonia over an extended period (10-60 d) at room temperature. It was done without agitation at atmospheric pressure. SAA treatment removed 55-74% of the lignin, but retained nearly 100% of the glucan and 85% of the xylan. The xylan remaining in the corn stover after SAA treatment was hydrolyzed along with the glucan by xylanase present in the Spezyme CP enzyme. In the simultaneous saccharification and fermentation (SSF) test of SAA-treated corn stover, using S. cerevisiae (D5A), an ethanol yield of 73% of theoretical maximum was obtained on the basis of the glucan content in the treated corn stover. The accumulation of xylose in the SSF appears to inhibit the cellulase activity on glucan hydrolysis, which limits the yield of ethanol. In the simultaneous saccharification and co-fermentation (SSCF) test, using recombinant E. coli (KO11), both the glucan and xylose were effectively utilized, resulting in on overall ethanol yield of 77% based on the glucan and xylan content of the substrate. When the SSCF process is used, the fact that the xylan fraction is retained during pretreatment is a desirable feature since the overall bioconversion can be carried out in a single step without separate recovery of xylose from the pretreatment liquid.

Potential of Agricultural Residues and Hay for Bioethanol Production

“…All samples were centrifuged at 5,000×g for 10 min before analysis. The ethanol yield was calculated as a percentage of theoretical maximum ethanol yield (Y max ) as per Equation (1) [15].…”

“…However, depending on the origin of the biomass, pretreatment methods applied, and yeast culture used, the ethanol yield can vary greatly from 31 to 84% of the theoretical maximum value for wheat straw [9][10][11][12] and 58 to 88% for corn stover [15][16][17][18]. It is, therefore, necessary to develop conversion methods for various feedstocks based on optimum pretreatment, hydrolysis, and fermentation conditions.…”

Application of Response Surface Methodology to Optimize Alkali Concentration, Corn Stover Particle Size, and Extruder Parameters for Maximum Sugar Recovery

“…When side chains of acetyl group present in hemicellulose are released, acetic acid is generated. Various researchers reported a range of 1.9-7.3% acetyl group for corn stover (Balan et al, 2009;Kim & Lee, 2005b;Torget et al, 1991;Weiss et al, 2009). Acetic acid was the only byproduct found in most of the pretreated corn stover samples in the range of 0.060-0.168 g/L.…”

Advances in consolidated bioprocessing systems for bioethanol and butanol production from biomass: a comprehensive review

“…Co-cultures or microbial consortia may also be utilized in the CBP systems as the third methodology. Brandon et al 2011Kang et al, 2010Kim et al, 2008Geddes et al, 2011Nieves et al, 2011Mullinnix, 2014Yang et al, 2014Jin et al, 2014 Jin et al 2012aOhgren et al 2006Wang et al, 2014aYasuda et al, 2014Zhu et al, 2014Fonseca et al, 2011Teixeira et al, 1999Jin et al, 2010Tang et al, 2011Zhang (J) et al, 2009Kim and Lee, 2005Zhang et al, 2012bYu et al, 2014Moreno et al, 2013Erdei et al, 2013aBallesteros et al, 2013Geddes et al, 2013Turhan et al, 2014Lan et al, 2013Hargreaves et al, 2013Alvira et al, 2011Olofsson et al, 2010a . In co-culture systems, saccharolytic and ethanologenic microorganisms are co-cultured to enhance efficient saccharification and fermentation in one pot.…”