Lignocellulosic Bioethanol Production: Advances in Genetic Engineering and Synthetic Biology

Global warming, decreasing air quality and declining oil reserves are the inevitable outcomes that result from the use of conventional fossil fuels, thus leading to the need to develop alternative fuels such as bioethanol. Current interest in bioethanol lies in production derived from lignocellulosic biomass due to the use of a renewable organic resource that does not compete with food supply. For bioethanol production to be economical, consolidated bioprocessing where the unit operations of pre-treatment, saccharification and fermentation occur in a single reaction vessel is under investigation as it offers several advantages over conventional multi-vessel operations. To realize consolidated bioprocessing, the tools of genetic engineering and synthetic biology have been utilized to revolutionize the modification of conventional yeast, Saccharomyces cerevisiae, so that it is able to consume a wide range of sugars apart from glucose, as well as tolerate harsh growing conditions in hydrolysates. However, non-conventional strains such as Kluyveromyces marxianus, Hansenula polymorpha and Pichia pistoris also have benefits, such as high ethanol tolerance, thermotolerance, and inhibitor tolerance, and synthetic biology is one of the tools used to improve these traits to achieve desired outputs. Synthetic biology utilizes the combination of biology and new designs, which have evolved from the huge amounts of data obtained from transcriptomics, proteomics, metabolomics, and fluxomics, to create novel synthetic pathways. Thus, this chapter highlights some successful advancements in genetic modifications tailored to the bioconversion of lignocellulosic biomass to ethanol.