Liquid-Liquid Extraction to Remove Saccharomyces cerevisiae Inhibitors: Incorporating with a Commercial Scale Biorefinery
Mahdieh Aghazadeh 1,2, Dr. Abigail S. Engelberth 1,2,3
1 Agricultural and Biological Engineering Department, Purdue University, West Lafayette, IN
2 Laboratory of Renewable Resources Engineering (LORRE), Purdue University, West Lafayette, IN
3 Division of Environmental and Ecological Engineering, Purdue University, West Lafayette, IN
The lignocellulosic biomass conversion process to bioethanol involves pretreating the woody structure of the biomass. Along with making the polymeric sugars more accessible for enzyme digestion, pretreatment steps release many other compounds (acids, furans, and phenolics) that can act as inhibitors for fermentation.
Our laboratory results show that liquid-liquid extraction removes most of the known inhibitors and reduce their concentration in the pre-fermentation broth below their inhibition threshold. Extensive studies have been performed to select an organic solvent with the lowest miscibility with the biomass liquid hydrolysate. The biocompatibility of the organic solvents with Saccharomyces cerevisiae strains (LNH-424A and NRRL Y-1546) has also been tested and ethyl acetate was selected as the solvent with highest biocompatibility and extractability.
Techno-economic analysis was performed to evaluate the practicality of the extraction system incorporation with an operating second-generation biorefinery. The results indicate compatibility with the biorefinery and that it is competitive with the other common separation techniques if the proposed solvent has high recovery ratio.
Adsorption experiments were designed and conducted to study the recovery potential of ethyl acetate from fermentation inhibitors. Commercially available adsorbents (i.e. activated carbon) at room temperature and low to medium agitation speeds were able to recycle almost 80% of the organic solvent back to the extraction stage.
The laboratory work, computer simulation, and techno-economic analysis results confirm the hypothesis that our system, consisting of ethyl acetate production reactor, extraction column, and adsorption unit, has the feasibility to be incorporated within a second generation bioethanol refinery.
Key words: fermentation inhibitors separation, liquid-liquid extraction, biocompatibility
See more of this Group/Topical: Separations Division