OPTIMIZATION OF SUGAR CONSUMPTION IN THE FERMENTATION OF TEMULOSE FOR ETHANOL PRODUCTION

Abstract

Temulose is a wastewater stream created in the production of medium-density fiberboard. It has a high sugar content, and therefore cannot be released into standard wastewater systems. Current methods for disposal of the wastewater stream involve concentrating it in an energy-intensive process and selling it as a cattle feed supplement, but with energy prices rising there is an incentive to find higher-value uses. The purpose of this study is to examine the feasibility of using Temulose as a substrate for industrial ethanol production, using sugar consumption rates to determine the success of a fermentation. Three organisms were studied: Zymomonas mobilis, NRRL B-806; Candida shehatae, NRRL Y-12858; and Saccharomyces cerevisiae. Shake-flask fermentations for Z. mobilis and C. shehatae were performed in triplicate for unamended, pH adjusted, and yeast extract amended Temulose at a sugar concentration of 20%. Fermentations with unamended Temulose showed little or no sugar consumption whatsoever, although the high sugar concentration of the Temulose may have affected the performance of the organisms. Fermentations with pH adjustment from 4.5 to 5.5 showed higher sugar consumption rates than yeast extract amended fermentations (1.16 mg/ml compared to 0.390 mg/ml for the first two days of fermentation). Additionally, Z. mobilis was shown to have higher rates of sugar consumption for both amended fermentations (1.02 mg/ml compared to 0.75 mg/ml for the first day). Fermentations using S. cerevisiae were performed with varying loading rates for yeast (0.5%, 1.0%, and 1.5%, w/v). Sugar consumption could not be determined, but ethanol concentrations up to 4% were observed after the first day of fermentation.