Tuesday, April 20, 2010
8-12

Cellulose solvent-based biomass saccharification: Phosphoric acid versus ionic liquid

Noppadon Sathitsuksanoh, Zhiguang Zhu, Xinhao Ye, and Y.-H. Percival Zhang. Biological Systems Engineering, Virginia Tech, 210-A Seitz Hall, Blacksburg, VA 24061

Efficient sugar release from biomass at competitive costs to those from corn and sugarcane still remains challenging.  Here we compared two cellulose solvent-based pretreatments, using phosphoric acid (COSLIF)1 and ionic liquid (IL)2 as cellulose solvents on corn stover.  Glucan digestibilities of COSLIF- and IL-pretreated corn stover were 89% and 48% at 5 FPUs of cellulase per gram of glucan, respectively.  It was found that ionic liquid removal efficiency from solid biomass was lower compared to that of phosphoric acid.  The remaining ionic liquid inhibited cellulase activity significantly.  Ionic liquid must be removed and recycled efficiently due to its high costs, enzyme inhibition, and negative impacts to the environment.  Therefore, it was necessary to completely wash ionic liquid from the pretreated cellulosic solids for better enzymatic hydrolysis and better economics of solvent recovery.  The phosphoric acid-based pretreatment yielded higher glucan digestibility because the remaining phosphate did not inhibit cellulase activity.  Moreover, COSLIF was believed to disrupt highly ordered hydrogen bonds of cellulose fibers more efficiently compared with IL pretreatment, thereby increasing more substrate accessibility, facilitating faster hydrolysis rates, and yielding higher digestibilities. High efficiency of recycling phosphoric acid is not necessary because the residual phosphate can be used as a nutrient for subsequent fermentation and used as phosphate fertilizers.  Our results suggested that phosphoric acid-based pretreatment was better than IL-based pretreatment.

[1] Sathitsuksanoh et al. Ind. Eng. Chem. Res. 2009, 48, 6441.
[2] Dadi et al. Biotechnol. Bioeng. 2006, 95, 904.



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