Novos transportadores de polióis em Debaryomyces hansenii

• Author(s): Pereira, Iliana Bento
• Date: 2011
• Persistent ID: http://hdl.handle.net/10400.5/4108
• Origin: Repositório da UTL
• Subject(s): lignocellulosic waste; bioethanol; polyols; debaryomyces hansenii
• Document Type: Master thesis
• Language: Portuguese
• Advisor(s): Prista, Catarina Geoffroy; Dias, Maria da Conceição Loureiro
• Contributor(s): Repositório da Universidade de Lisboa

Description

Mestrado em Engenharia Alimentar - Instituto Superior de Agronomia

Bioethanol production from lignocellulosic residues is a promising alternative for fossil fuels. However, it is still economically unviable due to the incapability of the main fermentative yeast, Saccharomyces cerevisiae, to ferment pentoses from hemicelluloses. In this work, a molecular approach was followed, as a contribution to construct genetically modified strains of S. cerevisiae expressing putative polyol transporters, in order to upgrade the hemicelluloses fermentation by producing simultaneously plus-valuable dietetical polyols for food industry, such as xylitol. A bibliographic screening for yeast species able to assimilate polyols revealed a restricted number of ascomycetes among the genus Candida, Debaryomyces and Pichia with potential interest as sinks of useful genes to improve polyol release. To identify polyol transporters, a BlastP search on D. hansenii CBS 767 genome was performed, followed by cloning and characterization in S. cerevisiae. The presence of polyol(sugar)/H+ symport activity was evaluated for 18 substrates based on the external alkalinization of unbuffered cell suspensions upon polyol(sugar) addition. In the present work 4 ORFs were cloned and 10 were characterized. Polyol/H+ symport activity (glycerol/H+, galactitol/H+, sorbitol/mannitol/ribitol/arabitol/H+) was detected in some of the strains tested.