(770e) Bioconversion of Water Hyacinth (Eichhornia crassipes) At Its Optimum Age Into Bioethanol Via Separate Hydrolysis and Fermentation With Continuous Overliming

This study explored the conversion of water hyacinth (Eichhornia crassipes) into bioethanol.  Prior to bioconversion into ethanol, the plant’s optimum age, or age (in days) at which its holocellulose to lignin content was highest, was determined to be 5 days on the average (leaf area ~ 64 cm²; average stem height ~ 10 cm).  At this stage, holocellulose content was highest at 76.3% and lignin content was lowest at 12.3%. Therefore, only five-day old plants were harvested for use in the rest of the experiments. Ethanol was produced from the lignocellulosic materials from the plant by hydrolysis, which breaks the cellulose and hemicellulose polymers to fermentable sugar, followed by fermentation which converts the sugar into ethanol. However, some byproducts such as furan compounds are released during hydrolysis and inhibit the yeast during fermentation. Hydrolysate detoxification using lime (‘overliming’) was employed. During batch detoxification, sudden addition of lime shows severe degradation of sugar simultaneously with furan compounds. Continuous detoxification was introduced in this study. Its optimum condition was determined to be at pH 12 and dilution rate of 0.667 hr^-1. Gradual addition of lime in continuous detoxification could keep the sugar concentration high enough at more than 90% with approximately similar detoxification levels of furan compounds. Using a traditional strain of S. cerevisiae, 12.7 g/L ethanol was produced. The ethanol yield per unit biomass was comparable to those reported in other agricultural biomasses: 0.151g/g dry biomass.