Abstract

Biofuels have received great attention as an alternative energy source mainly due to limited oil reserves. Bioethanol can be produced from wide range of raw materials like starch, sucrose and cellulosic based sources. Sugar beet and raw juice, as its intermediate product, constitute very profitable substrates for bioethanol production, considering content of easy available fermentable sugars. In this study, sugar beet pulp and raw juice were fermented with Saccharomyces cerevisiae distillery yeasts and bacterium Zymomonas mobilis. Different medium dilution rate as well as yeasts preparations (Fermiol, Safdistil C-70) were investigated. Fermentation was run for 72 h at 30°C. Quality of obtained raw distillates was evaluated using GC method. S. cerevisiae distillery yeasts turned out to be more favourable microorganism than bacterium Z. mobilis for sucrose material fermentation. The ethanol yield obtained from sugar beet pulp and raw juice was 84 and 95% of theoretical yield, respectively. Fermentation of sugar beet raw juice obtained by pressing without enzymatic treatment yielded higher ethanol efficiency as compared to raw juice pressed with enzyme. Dilution ratio 1:1 for fermentation medium appeared to be profitable for effective fermentation process.

Key words: Sugar beet roots, raw juice, fermentation, bioethanol, Saccharomyces cerevisiae, Zymomonas mobilis.