title: The introduction of the fungal D-galacturonate pathway enables the consumption of D-galacturonic acid by Saccharomyces cerevisiae.
abstract: BACKGROUND
  Pectin-rich wastes, such as citrus pulp and sugar beet pulp, are produced in considerable amounts by the juice and sugar industry and could be used as raw materials for biorefineries. One possible process in such biorefineries is the hydrolysis of these wastes and the subsequent production of ethanol. However, the ethanol-producing organism of choice, Saccharomyces cerevisiae, is not able to catabolize D-galacturonic acid, which represents a considerable amount of the sugars in the hydrolysate, namely, 18 % (w/w) from citrus pulp and 16 % (w/w) sugar beet pulp.
  
  
  RESULTS
  In the current work, we describe the construction of a strain of S. cerevisiae in which the five genes of the fungal reductive pathway for D-galacturonic acid catabolism were integrated into the yeast chromosomes: gaaA, gaaC and gaaD from Aspergillus niger and lgd1 from Trichoderma reesei, and the recently described D-galacturonic acid transporter protein, gat1, from Neurospora crassa. This strain metabolized D-galacturonic acid in a medium containing D-fructose as co-substrate.
  
  
  CONCLUSIONS
  This work is the first demonstration of the expression of a functional heterologous pathway for D-galacturonic acid catabolism in Saccharomyces cerevisiae. It is a preliminary step for engineering a yeast strain for the fermentation of pectin-rich substrates to ethanol.
authors.affiliation: Departamento de Bioquímica e Biologia Molecular, Universidade Federal do Paraná, Cx. P. 19046 Centro Politécnico, Curitiba, PR, 81531-980, Brazil. ext-alessandra.biz@vtt.fi.|VTT Technical Research Centre of Finland Ltd, P.O. Box 1000, 02044 VTT, Espoo, Finland. ext-alessandra.biz@vtt.fi.
authors.forename: Alessandra
authors.identifier: http://orcid.org/0000-0001-6736-953X
authors.initials: A
authors.lastname: Biz
authors.affiliation: Departamento de Bioquímica e Biologia Molecular, Universidade Federal do Paraná, Cx. P. 19046 Centro Politécnico, Curitiba, PR, 81531-980, Brazil.|Departamento de Engenharia Química e Engenharia de Alimentos, Universidade Federal de Santa Catarina, Cx. P. 476 Campus Reitor João David Ferreira Lima, Florianópolis, SC, 88040-970, Brazil.
authors.forename: Maura Harumi
authors.initials: MH
authors.lastname: Sugai-Guérios
authors.affiliation: VTT Technical Research Centre of Finland Ltd, P.O. Box 1000, 02044 VTT, Espoo, Finland.
authors.forename: Joosu
authors.initials: J
authors.lastname: Kuivanen
authors.affiliation: VTT Technical Research Centre of Finland Ltd, P.O. Box 1000, 02044 VTT, Espoo, Finland.
authors.forename: Hannu
authors.initials: H
authors.lastname: Maaheimo
authors.affiliation: Departamento de Química, Universidade Federal do Paraná, Cx. P. 19081 Centro Politécnico, Curitiba, PR, 81531-980, Brazil.
authors.forename: Nadia
authors.initials: N
authors.lastname: Krieger
authors.affiliation: Departamento de Bioquímica e Biologia Molecular, Universidade Federal do Paraná, Cx. P. 19046 Centro Politécnico, Curitiba, PR, 81531-980, Brazil.
authors.forename: David Alexander
authors.initials: DA
authors.lastname: Mitchell
authors.affiliation: VTT Technical Research Centre of Finland Ltd, P.O. Box 1000, 02044 VTT, Espoo, Finland. peter.richard@vtt.fi.
authors.forename: Peter
authors.initials: P
authors.lastname: Richard
mesh_terms: D001234:Aspergillus niger / Q000235:genetics; D027461:Beta vulgaris; D002957:Citrus; D000431:Ethanol / Q000378:metabolism; D005285:Fermentation; D005632:Fructose / Q000378:metabolism; D006603:Hexuronic Acids / Q000378:metabolism*; D006868:Hydrolysis; D060847:Metabolic Engineering / Q000379:methods; D053858:Metabolic Networks and Pathways / Q000235:genetics*; D009492:Neurospora crassa / Q000235:genetics; D010368:Pectins / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000235:genetics* / Q000378:metabolism*; D014242:Trichoderma / Q000235:genetics
chemical_list: D006603:Hexuronic Acids; D005632:Fructose; D000431:Ethanol; C007819:galacturonic acid; D010368:Pectins
keywords: Citrus pulp; D-galacturonic acid; Ethanol; Metabolic engineering; Saccharomyces cerevisiae