Bioethanol is currently the most widely used liquid biofuel. However, most of the bioethanol is made from conventional raw materials such as corn, grain or sugar cane. These raw materials rich in sugar and starch are expensive and their use competes with the food and feed sector. For this reason, lignocellulosic biomass is an interesting low-cost alternative due to its wide availability, its high sugar content (up to 75% of the total dry weight), and its non-competition with the food and feed sector. The global production of lignocellulosic bioethanol is still low due to the recalcitrant nature of lignocellulose and the presence of a mixture of 5 and 6 carbon sugars. Glucose and xylose are the main monosaccharides present in lignocellulosic hydrolysates, and their complete fermentation is key to achieve high overall ethanol yields. However, most fermentative microorganisms use glucose before xylose due to the higher affinity for glucose in their transport system.
In this work*, 18 clones of the yeast Candida intermedia, showing three different cell morphologies, were isolated and characterized in co-culture with Saccharomyces cerevisiae in a medium with lignocellulosic hydrolysate. Subsequently, one of the clones called C. intermedia CBS 141442 was selected and its fermentation performance was investigated under different process configurations. The results obtained demonstrated the potential of C. intermedia as a glucose and xylose co-fermenting microorganism in bioethanol production processes from lignocellulosic raw materials.
This work was carried out in collaboration with researchers from CIEMAT (Madrid, Spain) and Chalmers University of Technology (Gothenburg, Sweden), all of them top-level scientists in the application of yeasts in different biotechnological processes.
(*) Moreno, A.D., Tomás-Pejó, E., Olsson, L., Geijer, C. Candida intermedia CBS 141442: A novel glucose/xylose co-fermenting isolate for lignocellulosic bioethanol production. (2020) Energies, 13 (20), art. no. 5363. DOI: 10.3390/en13205363
More information: Elia Tomás Pejó, Senior Assistant Researcher, Biotechnological Processes Unit. firstname.lastname@example.org
Different cell morphologies of C. intermedia grown on xylose media