Genetic Regulation of Principal Microorganisms (Yeast, Zymomonas mobilis, and Clostridium thermocellum) Producing Bioethanol/Biofuel

Interest in ethanol production has been increasing since the 1980s because it is considered an alternative source of clean energy. The search for new and cheaper raw materials drove the development of new processes to obtain ethanol, such as the fermentation of lignocellulosic hydrolysates. In lignocellulosic ethanol production, microbial cells are under a stress-inducing environment, and their physiological behavior is altered significantly, indicating that different gene regulatory mechanisms are activated from those in non-stress-inducing conditions. Ethanologenic yeasts and bacteria tune gene expression to regulate response mechanisms and quickly adapt their global metabolic networks to grow and produce ethanol under unfavorable circumstances. Understanding the regulatory mechanism of gene expression during ethanol production has been a main topic in molecular and cellular biology with the goal of developing more efficient and resistant ethanol-producing microorganisms. In this chapter, we present the state of knowledge in the field of genetic regulatory mechanisms in the most important microorganisms used for ethanol production, the yeasts Saccharomyces cerevisiae and Kluyveromyces marxianus, and the bacteria Zymomonas mobilis, and Clostridium thermocellum.