Perspectives on current and future yeast technologies for ethanol-based biofuels and bioproducts

Greenhouse gases drive climate change, which leads to less productive farmland and diminishing food security. Fossil oil, which is used for transport fuels and for manufacturing plastics, synthetic fabrics and other everyday products, is a major contributor to climate change. Significant greenhouse gas abatement can be achieved by replacing fossil oil with renewable biofuels. Bioethanol is proven as a road transport fuel and has potential to be converted into sustainable aviation fuel and chemicals currently made from oil. First-generation (1G) bioethanol is produced by yeast fermentation of six-carbon sugars from food crops, and it represents the major biofuel by volume. A growing second-generation (2G) industry produces bioethanol via yeast fermentation of six- and five-carbon lignocellulosic sugars. This article considers yeast-dependent aspects of 1G and 2G technologies. Critical phenotypes essential for bioethanol processes are reviewed along with classical and molecular genetic strategies for yeast strain improvements. Bioethanol production needs to be increased substantially to approach full fossil oil replacement. The future for bioethanol and the role of yeasts in mitigating climate change and improving land-use are discussed in terms of third- and fourth-generation bioethanol, and multiproduct Power-to-X biorefineries that include potential for carbon dioxide fixation by yeasts.