Potential of Thermo-tolerant Microorganisms for Production of Cellulosic Bioethanol

Production of biofuels from renewable feedstocks has received much scientific attention since the biofuels can be used for energy and alternative fuel supplies, and cellulose-based sources as second-generation biomass generally do not compete with food. However, biofuels derived from second-generation biomass produced by conventional technology are very expensive compared to biofuels derived from first-generation biomass, and the development of innovative technologies is therefore essential to significantly reduce costs. One possible technology is high-temperature fermentation technology, which is expected to reduce cooling costs, improve efficiency of simultaneous saccharification and fermentation, minimize contamination risk, and stabilize fermentation. This chapter addresses the production of cellulosic bioethanol using the potential of the thermotolerant yeast Kluyveromyces marxianus through different process configurations including separate hydrolysis and fermentation, simultaneous saccharification and fermentation, consolidated bioprocessing, and simultaneous saccharification, fermentation, and distillation. We also introduce improvements of thermotolerant yeasts by laboratory adaptation and mutagenesis for cellulosic bioethanol production as well as the principle and effectiveness of a membrane separation technology that can be linked to high-temperature fermentation for process intensification in bioethanol production.