Fermentation, the third step of bioconversion, con­verts the hydrolysates, mainly glucose, xylose, arabinose

and mannose to bioethanol using microorganisms. In addition to bioethanol, fermentation can be used to generate other useful end products, e. g. biobutanol, fatty acids, lactic acid, bioplastics or other biochemicals. The hydrolysates are often detoxified before fermentation due to the production of inhibitory compounds, such as phenolics and furan derivatives, in the pretreatment and hydrolysis steps (Dashtban et al., 2009; Ong, 2004). Saccharomyces cerevisiae is the most commonly used microorganism as it has a high fermentation rate and the application of recombinant DNA techniques has enabled the bioengineering of strains, capable of converting arabinose and xylose, as well as glucose, to bioethanol (Dashtban et al., 2009). This allows utilization of a larger amount of the hydrolysates, thus giving a higher percentage yield of bioethanol.