This Article
Right arrow Full Text
Right arrow Full Text (PDF)
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Services
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrowReprints and Permissions
Right arrow Copyright Information
Right arrow Books from ASM Press
Right arrow MicrobeWorld
Citing Articles
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Vidgren, V.
Right arrow Articles by Londesborough, J.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Vidgren, V.
Right arrow Articles by Londesborough, J.
Agricola
Right arrow Articles by Vidgren, V.
Right arrow Articles by Londesborough, J.

 Previous Article  |  Next Article 

Applied and Environmental Microbiology, April 2009, p. 2333-2345, Vol. 75, No. 8
0099-2240/09/$08.00+0     doi:10.1128/AEM.01558-08
Copyright © 2009, American Society for Microbiology. All Rights Reserved.

Improved Fermentation Performance of a Lager Yeast after Repair of Its AGT1 Maltose and Maltotriose Transporter Genes{triangledown} ,{dagger}

Virve Vidgren, Anne Huuskonen, Hannele Virtanen, Laura Ruohonen, and John Londesborough*

VTT Technical Research Centre of Finland, P.O. Box 1000, FI-02044 VTT, Finland

Received 9 July 2008/ Accepted 21 January 2009

The use of more concentrated, so-called high-gravity and very-high-gravity (VHG) brewer's worts for the manufacture of beer has economic and environmental advantages. However, many current strains of brewer's yeasts ferment VHG worts slowly and incompletely, leaving undesirably large amounts of maltose and especially maltotriose in the final beers. {alpha}-Glucosides are transported into Saccharomyces yeasts by several transporters, including Agt1, which is a good carrier of both maltose and maltotriose. The AGT1 genes of brewer's ale yeast strains encode functional transporters, but the AGT1 genes of the lager strains studied contain a premature stop codon and do not encode functional transporters. In the present work, one or more copies of the AGT1 gene of a lager strain were repaired with DNA sequence from an ale strain and put under the control of a constitutive promoter. Compared to the untransformed strain, the transformants with repaired AGT1 had higher maltose transport activity, especially after growth on glucose (which represses endogenous {alpha}-glucoside transporter genes) and higher ratios of maltotriose transport activity to maltose transport activity. They fermented VHG (24° Plato) wort faster and more completely, producing beers containing more ethanol and less residual maltose and maltotriose. The growth and sedimentation behaviors of the transformants were similar to those of the untransformed strain, as were the profiles of yeast-derived volatile aroma compounds in the beers.

* Corresponding author. Mailing address: VTT Technical Research Centre of Finland, P.O. Box 1000, FI-02044 VTT, Finland. Phone: 358 20 722 5996. Fax: 358 20 722 7071. E-mail: john.londesborough{at}vtt.fi

{triangledown} Published ahead of print on 30 January 2009.

{dagger} Dedicated to the memory of Isabel Spencer-Martins, a yeast scientist who made a great contribution to our knowledge of sugar transport.

Applied and Environmental Microbiology, April 2009, p. 2333-2345, Vol. 75, No. 8
0099-2240/09/$08.00+0     doi:10.1128/AEM.01558-08
Copyright © 2009, American Society for Microbiology. All Rights Reserved.





Copyright © 2009 by the American Society for Microbiology.   For an alternate route to Journals.ASM.org, visit: http://intl-journals.asm.org | More Info»