| In using a bioprocess to produce ethanol from renewable resources through acid hydrolysis, the hydrolyzate by-products and extract solvents can inhibit the fermentation. The purpose of this research was to measure the inhibitory effects of representative hydrolyzate constituents (acetophenone, 1-hexanol, and hexane) on fermentation using Saccharomyces cerevisiae and Zymomonas mobilis. It was found that these two microorganisms were comparable in their ability to tolerate the hydrolyzate constituents, although Z. mobilis seemed more sensitive to inhibitors than S. cerevisiae at higher hydrolyzate by-product concentrations or when three hydrolyzate constituents coexisted in the medium.;The limiting concentrations of the hydrolyzate constituents were decided. Among these three materials, 1-hexanol was the most serious inhibitor, while hexane was the least one. The immobilized cell reactor could endure a higher concentration of hydrolyzate constituents than the batch reactor. It was also found that the presence of low concentration of hydrolyzate constituents was beneficial in alleviating cell overgrowth in cross-linked immobilized cell reactors. Mathematical models were developed to predict the effects of acetophenone concentration at various inoculum sizes on growth and substrate uptake in batch culture. |
