enzymatic hydrolysis of the cellulose into monomeric sugars. The enzymatic hydrolysis
step is a vital process in the production of ethanol from biomass. Standard procedure for
removing inhibitory bioproducts prior to enzymatic hydrolysis is to wash the pretreated
biomass,with up to 30 volumes of water, a process not effective beyond the lab-scale
experiments.
Our research focused on quantifying differences in yields of both glucose and ethanol
from dilute acid pretreated biomass samples, with one sample being washed and one
not. Biomass was high-density poplar selected for its wide availability and potential as
a future biomass source. Pretreatment process was carried out at 140°C for 40 min
in a 1-L Parr reactor with 0.98% (v/v) sulfuric acid. Enzyme hydrolysis was carried out
with Accellerase®1500 (Genencor) at 50 °C for 24 hours. Fermentation was performed
in 50-mL shake flasks with two different strains of yeast (SPSC01 and a standard
Saccharomyces cerevisiae strain AJCC4126).
HPLC analysis of hydrolysates from washed and unwashed samples showed presence
of similar compounds at different concentrations. Glucose yield from washed sample was
5.3 times higher than yield from unwashed; whereas, concentrations of inhibitors such
as furfural were lower for washed sample than unwashed. Similarly, hydrolysates from
washed sample yielded higher ethanol concentration than hydrolysates from unwashed
samples. This work demonstrates that even small amounts of washing can play a
significant role in affecting yields in the biomass to ethanol conversion process.