Investigating the membrane transport and assimilation of L-arabinose and xylose by the yeasts Aureobasidium leucospermi LB86, Candida oleophila G10.1, Issachenkia terricola G20 and Pichia guilliermondii G1.2
The fermentation of pentoses is an essential step to improve the production yield of ethanol and organic acids from the degradation of plant biomass. In view of this, many efforts have been made to hydrolyze the hemicellulosic material and the consequent fermentation of pentoses derived from this process. However, the large contingent of hemicellulose has been little used in fermentative processes. Much of this is justified by the difficulty of many yeasts in assimilating pentoses derived from this polysaccharide. Studies in metabolic engineering have shown that yeasts, such as Saccharomyces cerevisae, even modified for the assimilation of pentoses, have not been able to present satisfactory yield in the assimilation of these sugars. In view of this, in this project, we propose to investigate more deeply some yeasts as to their capacity for the assimilation of L-arabinose and D-xylose, namely: Aureobasidium leucospermi LB86, Candida oleophila G10.1, Issachenkia terricola G20 and Pichia guilliermondii G1.2. In the results obtained so far, we have observed that these yeasts are able to grow by assimilating arabinose and xylose as the only sources of carbon in both acid and neutral medium. This gives us an indication for the subsequent use of these yeasts for fermentation of arabinose and xylose from the acid hydrolysis of hemicellulose. In view of these results, it is agreed that the assimilation of pentoses and the microbial growth using these sugars implies the existence of an efficient system of transport through the membrane. With this in mind, we believe in the need to investigate this mechanism of membrane transport in order to improve the utilization of these sugars resulting from the hydrolysis of vegetal biomass. For the accomplishment of these studies, we have a partnership established with Prof. Dr. Catarina Prista, from the Microbial Bioenergy Laboratory, CBAA, Higher Institute of Agronomy, Lisbon, Portugal. The choice of this partnership is justified by the experience and excellence of research in this segment of membrane transport in yeasts and by the structure offered by this research center. In granting this postdoctoral fellowship (2017 / 06399-3), we had already mentioned the need to carry out this internship abroad. Our intention is to investigate the kinetics of membrane transport and the transporters involved in this system of pentoses transport, in order to provide subsidies to the metabolic engineering researches of these and other yeasts. During the realization of this project we hope to obtain differentiated results, and at the end of the work, contribute to the advancement in the knowledge on the assimilation of yeast pentoses and improve methodologies for the use of arabinose and xylose derived from hemicellulose.
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