(642f) Liquid-Liquid Extraction to Remove Saccharomyces Cerevisiae Inhibitors: Incorporating with a Commercial Scale Biorefinery

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