Dr Michelle Walker

Dr Michelle Walker
  • Qualifications

    Bachelor of Science (Honours) in Agricultural Biochemistry, University College of Wales, Aberystwyth, Wales (1983)

    PhD in Microbiology, University of Edinburgh, Scotland (1988)

  • Research Interests

    Broad Research Interest: 

    Wine microbes (Saccharomyces cerevisiae, non-Saccharomyces and Lactic Acid Bacteria) - fundamental and applied research

    Specific Project Areas: 

    Bioprospecting for non-Saccharomyces and lactic acid bacteria with novel attributes beneficial to winemaking

    Strategies to generate wine yeast with improved fermentation capabilities (hybridisation, mutagenesis, adaptive evolution and CRISPR)

    Understanding the genetic basis for stress tolerance and fermentation attributes of wine yeast strains and their exploitation in strain improvement

    For more information go to: https://sciences.adelaide.edu.au/agriculture-food-wine/research/wine-food-nutrition-science/wine-microbiology-and-microbial-biotechnology-group

     

  • Publications

    Peer review papers:

    González Alonso, I., Walker, M. E., Vallejo Pascual, M. E.,  Naharro Carrasco, G., Jiranek, V. Capturing yeast associated with grapes and spontaneous fermentations of the Negro Saurí minority variety from an experimental vineyard near León. Scientific Reports 11, 3748 (2021). https://doi.org/10.1038/s41598-021-83123-1

     

    Walker, M.E., Zhang, J., Sumby, K., Lee, A., Houlès, A., Li, S J., Jiranek, V. Sulfate transport mutants affect hydrogen sulfide and sulfite production during alcoholic fermentation. Yeast. 2021. Accepted Author Manuscript. https://doi.org/10.1002/yea.3553

    Lin, M. M-H., Boss, P. K., Walker, M. E., Sumby, K. M., Grbin, P. R., Jiranek, V. (2020)  Evaluation of indigenous non-Saccharomyces yeasts isolated from a South Australian vineyard for their potential as wine starter cultures. International Journal of Food Microbiology. doi.org/10.1016/j.ijfoodmicro.2019.108373

    Pilkington, L., Deed, R., Parish-Virtue, K., Huang, C-W., Walker, M., Jiranek, V., Barker, D., Fedrizzi, B. (2019) Alterative synthetic strategies and gene deletant experiments enable the first identification of polysulfides in Saccharomyces cerevisiae. Chemical Communications 60 doi: 10.1039/c9cc03020d

    Valentine, G.D.S., Walker, M.E., Gardner, J.M., Schmid, F., Jiranek, V. Brief temperature extremes during wine fermentation: effects on yeast viability and fermentation progress. Australian Journal of Grape and Wine Research doi: 10.1111/ajgw.12365

    Peter, J.J., Watson, T., Walker, M.E., Gardner, J.M., Lang, T.A., Borneman, A., Forgan, A., Tran, T. and V. Jiranek. (2018) Use of wine yeast deletion collection reveals genes that influence fermentation performance under low nitrogen conditions.  FEMS Yeast Research 18(3) doi: 10.1093/femsyr/foy009.

    Zhang, J., Astorga, M.A., Gardner, J.M., Walker, M.E., Grbin, P.R., Jiranek, V. (2018) Disruption of the cell wall integrity gene ECM33 results in improved fermentation by wine yeast. Metabolic Engineering 45, 255-264.

    Nguyen, T. D., Walker, M. E., Gardner, J.M., and Jiranek, V. (2017) Appropriate vacuolar acidification in Saccharomyces cerevisiae is required for efficient high sugar fermentation. Food Microbiology 70: https://doi.org/10.1016/j.fm.2017.09.021

    Huang, C-W., Walker, M., Fedrizzi, B., Roncoroni, M., Gardner, R. and Jiranek, V. (2017) Hydrogen sulfide and its roles in Saccharomyces cerevisiae in a winemaking context. FEMS Yeast Research 17(6): doi: 10.1093/femsyr/fox058.

    Huang, C-W., Walker, M., Fedrizzi, B., Roncoroni, M., Gardner, R. and Jiranek, V. (2017) Yeast genes involved in regulating cysteine uptake affect production of hydrogen sulfide from cysteine during fermentation. FEMS Yeast Research 17(5)  doi: 10.1093/femsyr/fox046

    Huang, C-W., Walker, M., Fedrizzi, B., Roncoroni, M., Gardner, R. and Jiranek, V. (2016) The yeast TUM1 affects production of hydrogen sulfide from cysteine treatment during fermentation. FEMS Yeast Research 16 (8): fow100. doi: 10.1093/femsyr/fow100

    Walker, M. E., Nguyen, T. D., Liccioli, T., Schmid, F., Kalatzis, N., Sundstrom, J. F., Gardner, J. M., and Jiranek, V. (2014) Genome-wide identification of the fermentome; genes required for successful and timely completion of fermentation by Saccharomyces cerevisiae. BMC Genomics 15:552  doi:10.1186/1471-2164-15-552 Published: 3 July 2014 http://www.biomedcentral.com/1471-2164/15/552 

    Capaldo, A., Walker, M.E., Ford, C.F., and V. Jiranek (2011) beta-Glucoside metabolism in Oenococcus oeni: Cloning and characterisation of the phospho-beta-glucosidase bgID. Food Chemistry, 125(2):476-482

    Liccioli, T., Walker, M.E., Sundstrom, J.F., Gardner, J.M., and Jiranek, V. (2013)
    Novel wine yeast for improved  performance in fermentationWine & Viticulture Journal  28 (6): 30-33

    Capaldo, A., Walker, M.E., Ford, C.F., and V. Jiranek (2011) β-Glucoside metabolism in Oenococcus oeni: cloning and characterization of the phospho-β-glucosidase CelD. Journal Molecular of Catalysis B: Enzymatic, 69(1-2):27-34

    Poole, K.A., Walker, M.E., Warren, T., Gardner, J. M., McBryde, C.M., de Barros Lopes, M., and  V. Jiranek (2009) Proline transport and stress tolerance of ammonia-insensitive mutants of the PUT4-encoded proline-specific permease in yeast. Journal of General and Applied Microbiology, 55(6):427-439

    Astorga, A.M., Gardner, J.M., McBryde, C., Schmid, F., Walker, M.E., and V. Jiranek (2007) Optimisation of industrial strains of Saccharomyces cerevisiae using recombinant and non-recombinant methods. Microbiol. Aust.25 62-63

    Walker, M.E., Vystavelova, A., Pedler, S., Eglington, J. and V. Jiranek (2005) PCR-based gene disruption and recombinatory marker excision to produce modified industrial Saccharomyces cerevisiae without added sequences. J. Microbiol. Methods 63 193-204

    Matthews, A., Grimaldi, A., Walker, M.E., Bartowsky, E., Grbin, P. and V. Jiranek (2004) Lactic Acid Bacteria as a Potential Source of Enzymes for Use in Vinification. Appl. Environ. Microbiol. 70(10) 5715-5731

    Walker, M.E., Gardner, J.M., Vystavelova, A., McBryde, C., des Barros Lopes, M. and V. Jiranek (2003) Application of the reuseable, KanMX selectable marker to industrial yeast: construction and evaluation of heterothallic wine strains of Saccharomyces cerevisiae, possessing minimal foreign DNA sequences. FEMS Yeast Research 4(3) 339-347

    Walker, M.E., Gardner, J.M., des Barros Lopes, M. and V. Jiranek (2002)Wine yeasts as tools for oenological research and strain improvement by genetic techniques. The Australian & New Zealand Grapegrower & Winemaker, Annual Technical Issue. 406a 109-115

    Jitrapakdee, S., Walker, M.E. and J.C. Wallace (1999) Functional Expression, Purification, and Characterization of Recombinant Human Pyruvate CarboxylaseBiochem. Biophys. Res. Commun. 266 512-517

    Jitrapakdee, S., Walker, M.E. and J.C. Wallace (1996) Identification of Novel Alternatively Spliced Pyruvate Carboxylase mRNAs with Divergent 5' -Untranslated Regions Which Are Expressed in a Tissue-Specific Manner.Biochem. Biophys. Res. Commun. 223 695-700

    Val, D.L., Chapman-Smith, A., Walker, M.E., Cronan, J.E., and J.C. Wallace (1995) Polymorphism of the yeast pyruvate carboxylase 2 gene and protein: Effects on biotinylation. Biochem. J. 312 817-825

    Walker, M.E., Baker, E., Wallace, J.C.. & G.R. Sutherland (1995)Assignment of the human pyruvate carboxylase gene (PC) to 11q13.4 by fluorescence in situ hybridisation. Cytogenetics and Cell Genetics 69 187-189

    Brewster, N.K., Val, D.L., Walker, M.E. & J.C. Wallace (1994) Regulation of pyruvate carboxylase isoenzyme (PYC1PYC2) gene expression inSaccharomyces cerevisiae during fermentative and non-fermentative growth.Arch. Biochem. Biophys. 311(1) 62-71

    Walker, M.E., Val, D.L., Rohde, M., Devenish, R.J. & J.C. Wallace (1991) Yeast pyruvate  carboxylase: Identification of two genes encoding isoenzymes.  Biochem. BiophysRes. Commun. 176 (3) 1210-1217

    Walker, M.E. & J.C. Wallace (1991) Isolation of a yeast mutant deficient in pyruvate carboxylase activity. Biochem. Int23(4) 697-705

     

    Industry Articles:

    Walker, M.E., Gardner, J.M., des Barros Lopes, M. and V. Jiranek (2002) Wine yeast as tools for oenological research and strains improvement by genetic techniques.  The Australian & New Zealand Grapegrower & Winemaker, Annual Technical Issue.  461a 109-114

    Liccioli, T., Walker, M.E., Sundstrom, J.F., Gardner, J.M. and V. Jiranek (2013) Novel wine yeast for improved performance in fermentation. Wine and Viticulture J. http://winetitles.com.au/wvj/

    Walker, M.E., Sundstrom, J.F., Liccioli, T., Dillon, S., Long, D., Nguyen, T., Tek, E-L. and J. Zhang (2014)  Adelaide researchers head ‘over the ditch’ for Australisian yeast meeting. Grapegrower and Winemaker March 2014 - Issue 603. www.winebiz.com.au 

    Walker, M.E., Gardner, J., Liccioli, T. and V. Jiranek (2014) Tackling microbial failure in problematic wine fermentations using a holistic approach.  Grapegrower and Winemaker April 2014 - Issue 604.  www.winebiz.com.au

    Gardner, J. M., Walker, M. E., Boss, P. K. and V. Jiranek (2020) Is juice dilution your solution? How do microbes feel about it? Wine and Viticulture J. 1, 22-28

    Gardner, J. M., Walker, M.E., Zhang, J., van Holst, N. and V. Jiranek (2020) Searching new frontiers for winemaking microbes with unusual and useful activities.  Australian and New Zealand Grapegrower and Winemaker 680, 87-88. 

     

    Conference Abstracts (since 2000)

    (Presenting Author in bold) 

    2001  11th Australian Wine Industry Technical Conference (Adelaide)

    Poster: “Construction and evaluation of haploid wine yeast for research purposes” M.E. Walker, Gardner, J.M., and V. Jiranek

    2002  2nd Australian Conference on Yeast: Products and Discovery (Melbourne)

    Poster:”Development of Heterothallic Wine Yeast Strains for Oenological Research” M.E. Walker, Gardner, J, Vystavelova, A., and V. Jiranek

    2004  12th Australian Wine Industry Technical Conference (Melbourne)

    Walker, M., Vystavelova, A., Pedler, S., Eglinton, J., and Jiranek, V. (2004) Towards tools for ‘seamless’ modification of genes in industrial yeast. Proc. 12th Aust. Wine Ind. Tech. Conf. July, 2004, Melbourne. p 290.

    2007  23rd International Conference on Yeast Genetics and Molecular Biology (Melbourne)

    Poster: “Screening of transposon mutation libraries in a wine yeast background to identify genes contributing to successful fermentation” M.A. Astorga., Gardner, J.M., Walker, M.E., de Barros Lopes, M., andV. Jiranek

    2007  23rd International Conference on Yeast Genetics and Molecular Biology (Melbourne)

    Poster: “Strategies for the Generation of Wine Yeast Strains with Novel Fermentation Traits” M.E. Walker, Gardner, J.M., McBryde, C., Schmid, F., Macintyre, A., Bishop, A., and V. Jiranek

    2007  23rd International Conference on Yeast Genetics and Molecular Biology (Melbourne)

    Poster: “An automated fermentation system for evaluation of large numbers of yeast strains in laboratory wine fermentations” F. Schmid,Walker, M.E., and V., Jiranek

    2007 23rd International Conference on Yeast Genetics and Molecular Biology (Melbourne)

    Poster: “Screening of a mutagenic transposon library in a wine yeast background to identify genes contributing to successful fermentation”J.M. Gardner, A.M. Astorga, M.E. Walker and V. Jiranek

    2007 13th Australian Wine Industries Technical Conference (Adelaide)

    Poster: Strategies for the Generation of Wine Yeast Strains with Novel Fermentation Traits” M.E. Walker, Gardner, J.M., McBryde, C., Schmid, F., Macintyre, A., Bishop, A., and V. Jiranek

    2007  13th Australian Wine Industries Technical Conference (Adelaide)

    Poster: “Construction and of wine yeast with increased tolerance to osmotic stress and their evaluation under wine fermentation” N. Lam, Walker, M. E., and V. Jiranek

    2007  13th Australian Wine Industries Technical Conference (Adelaide)

    Poster: “An automated fermentation system for evaluation of large numbers of yeast strains in laboratory wine fermentations” F. Schmid,Walker, M.E., and V., Jiranek

    2007  13th Australian Wine Industries Technical Conference (Adelaide)

    Poster:  “Expression and characterisation of a β-glucosidase gene from Oenococcus oeni for oenological use” A. Capaldo, M.E. Walker, C. Ford and V. Jiranek,

    2009  24th International Conference on Yeast Genetics and Molecular Biology (Manchester)

    Poster:  “The influence of wine yeast on colour extraction and stabilisation in red wine” M.E. Walker, Liccioli, T., Warren, T., Capaldo, A., Schmid, F., and V. Jiranek

    2009  24th International Conference on Yeast Genetics and Molecular Biology (Manchester)

    Poster: “Adaptive evolution strategies for the generation of novel wine yeast”

    McBryde,  C., Gardner, J.M.,  Walker, M.E., and V. Jiranek

    2009  24th International Conference on Yeast Genetics and Molecular Biology (Manchester)

    Poster: “Enzymatic activities of Lactic Acid Bacteria: Distribution, cloning and characterisation of esterases and glycosidases” K. Sumby, Capaldo, A., Walker, M.E., Grbin, P., Ford, C. and V. Jiranek

    2009  4th Australian conference on Yeast: Products and Discovery (Adelaide)

    Talk: “Progress towards improvement of industrial yeast for the wine industry” M.E. WalkerGardner, J.M., Liccioli, T., Schmid, F., McBryde, C., and V. Jiranek

    2009  4th Australian conference on Yeast: Products and Discovery (Adelaide)

    Poster: “Progress towards characterisation of an adaptively evolved wine yeast strain” J.M. Gardner, McBryde, C.,  Walker, M.  and V Jiranek

    2010  14th Australian Wine Industries Technical Conference (Adelaide)

    Poster: “The identification of genes with the potential to influence wine colour and fermentation duration.” M. E. Walker, Liccioli, T., Schmid, F., Kalatzis, N., Gardner, J.M., Grbin, P.R. and V. Jiranek

    2011   Crush 2011 (Adelaide)

    Talk: “Identification and classification of Saccharomyces cerevisiaegenes required for high-sugar fermentation using a genome-wide screening approach” M.E. Walker, Liccioli, T., Schmid, F., Trung, D.N., Kalatzis, N., Sundstrom, J., Gardner, J.M., and V. Jiranek

    2011   School of Agriculture Food & Wine Research Day, University of Adelaide

    Talk: “Investigation of the genetic basis of high nitrogen efficiency (HNE) in wine yeast” J. Zhang, Gardner, J.M., Walker, M.E., Sundstrom, J.F., Grbin, P. and V. Jiranek 

    2012   Crush 2012 (Adelaide)

    Talk: “Investigation of the genetic basis of high nitrogen efficiency (HNE) in wine yeast” J. Zhang, Gardner, J.M., Walker, M.E. and V. Jiranek 

    2013   15th Australian Wine Industries Technical Conference (Sydney)

    Poster: “Second generation yeast with reduced hydrogen sulfide and sulfur dioxide

    production” M.E. Walker, Lee, A., Houlés, A., Adint, L., Li, S. and V. Jiranek

    2013   15th Australian Wine Industries Technical Conference (Sydney)

    Poster: “Genome screening as an approach to understand the cellular mechanisms behind yeast adaptation during fermentation to allow for successful completion”

    M. E. Walker, Liccioli, T., Schmid, F., Gardner, J. M., Kalatzis, N., Grbin, P. R. and V. Jiranek

    2013   15th Australian Wine Industries Technical Conference (Sydney)

    Poster: “Vacuolar acidification may play a key role in the ability of yeast to successfully complete industrial fermentation”

    T. D. Nguyen, Walker, M. E., Gardner, J. M., and V. Jiranek

    2013   15th Australian Wine Industries Technical Conference (Sydney)

    Poster: “Re-starting stuck wine fermentations using an evolved wine yeast. T.   Liccioli, Gardner, J., Walker, M., Sundstrom, J., Shearer, M. and V. Jiranek

    2013   15th Australian Wine Industries Technical Conference (Sydney)

    Poster: “Investigation of the genetic basis of high nitrogen efficiency (HNE) in wine yeast” J. Zhang, Gardner, J.M., Walker, M.E., Astorga, M.A., Sunstrom, J.,  Grbin, P. and V. Jiranek 

    2013   Australasian conference on Yeast: Products and Discovery (Auckland)

    Talk: Overexpression studies – an approach to understand the mechanisms behind successful alcoholic fermentation. M. Walker, Haggerty, J., Zhang, J., Nguyen, T. D., Sundstrom, J. Liccioli, T., Gardner, J. and V. Jiranek

    2013   Australasian conference on Yeast: Products and Discovery (Auckland)

    Talk: “Genome wide screening for the identification of genes influencing colour in red wine fermentations” T. Liccioli, Walker, M., Schmid, F., Kalatzis, N., Gardner, J., Grbin, P. and V. Jiranek.

    2013   Australasian conference on Yeast: Products and Discovery (Auckland)

    Talk: “Investigation and characterization of an High Nitrogen Efficient (HNE) wine yeast strain” J. Zhang, Gardner, J. M., Walker, M. E., Astorga, M. A., Grbin, P. and V. Jiranek.

    2013   Australasian conference on Yeast: Products and Discovery (Auckland)

    Poster: “Evaluation of fermentation efficiency of yeast Saccharomyces cerevisiae â–³tps1 and â–³tps2 deletants with over-expression of HXK2and TreA genes.” T. D. Nguyen, Walker, M. E., Gardner, J. M. and V. Jiranek

    2015   Oeno 2015: 10th International Symposium of Oenology of Bordeaux, (Bordeaux, France)

    Talk: “Generation and characterisation of improved wine microbes.”. Jiranek, V., Liccioli, T., Betteridge, A., Sumby, K., Walker, M., Gardner, J., Sundstrom, J.

    2015    Australasian conference on Yeast: Products and Discovery (Adelaide)

    Talk: “The impact of brief temperature shifts on wine fermentation.” Valentine, G.D.S., Walker, M., Gardner, J., Schmid, F. and V. Jiranek

    2015    Australasian conference on Yeast: Products and Discovery (Adelaide)

    Talk: “Screening for wine yeast mutants, whereby gene deletion results in faster fermentation under limited nitrogen conditions.” Peter, J.J., Watson, T., Walker, M., Gardner, J. and V. Jiranek

    2015    Australasian conference on Yeast: Products and Discovery (Adelaide)

    Talk: “Identification of yeast genes responsible for the production of hydrogen sulfide and volatile thiols in wine.” Huang, M, Gardner, R., Fedrizzi, B., Walker, M. and V. Jiranek

    2015   Australasian conference on Yeast: Products and Discovery (Adelaide)

    Talk: “Can further improvements be made in oenological traits of wine yeast?” Walker, M.E., Watson, T., Long, D., Lang, T., Zhang, J., Gardner, J.M. and V. Jiranek

    2015    Australasian conference on Yeast: Products and Discovery (Adelaide)

    Talk: “Screening for wine yeast mutants, whereby gene deletion results in faster fermentation under limited nitrogen conditions”

    Peter, J.J., Watson, T., Walker, M., Gardner, J. and V. Jiranek

    2015    Australasian conference on Yeast: Products and Discovery (Adelaide)

    Talk: “The impact of brief temperature shifts on wine fermentation”

    Valentine, G.D.S., Walker, M., Gardner, J., Schmid, F. and V. Jiranek

    2015   2015   Crush 2015 (Adelaide)

    Talk: Mapping of genes responsible for yeast-derived modulation of colour in model red wine

    Walker M., Watson, T., Roncoroni, M., Gardner, R. and V. Jiranek

    2016   14th International Congress on Yeasts (Awaji Island, Japan)

    Talk and Poster: “Identification of yeast genes responsible for the production of hydrogen sulfide (from cysteine) and volatile thiols in wine”

    Huang, M., Gardner, R., Fedrizzi, B., Walker, M. and V. Jiranek

    2016   14th International Congress on Yeasts (Awaji Island, Japan)

    Talk and Poster: “Mapping of genes responsible for yeast-derived modulation of colour in model

    red wine”

    Walker, M., Watson, T., Roncoroni, M, Gardner, R and V. Jiranek

    2018   ISSY34 34th International Specialized Symposium on Yeast (Bariloche, Argentina)

    E-Poster: “Investigation of yeast genes required for the modulation of colour in model red wine”

    Walker, M., Watson, T., Roncoroni, M, Huang, C-W, Gardner, R and V. Jiranek 

    2018   ISSY34 34th International Specialized Symposium on Yeast (Bariloche, Argentina)

    Talk: “Sulfate transport mutatns effect hydrogen sulphide production during alcoholic fermentation

    Walker, M., Zhang, J., Sumby, K., Lee, A., Houlès, A., Li, SJ, Watson, T. and V. Jiranek 

    2019    17th Australian Wine Industries Technical Conference (Adelaide)

    Poster: “Don’t like banana in your Riesling? Juice dilution might be your solution”

    Gardner, J., Walker, M., Boss, P. and V. Jiranek

     

     

      

     

  • Professional Associations

    Member of Australian Society of Viticulture and Oenology (2019 - present)

    Member of The Australasian Yeast Group (2009 - present)

The information in this directory is provided to support the academic, administrative and business activities of the University of Adelaide. To facilitate these activities, entries in the University Phone Directory are not limited to University employees. The use of information provided here for any other purpose, including the sending of unsolicited commercial material via email or any other electronic format, is strictly prohibited. The University reserves the right to recover all costs incurred in the event of breach of this policy.

Entry last updated: Saturday, 13 Feb 2021