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 fermentation. Wine & 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 Carboxylase. Biochem. 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 (PYC1, PYC2) 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. Biophys. Res. Commun. 176 (3) 1210-1217

  Walker, M.E. & J.C. Wallace (1991) Isolation of a yeast mutant deficient in pyruvate carboxylase activity. Biochem. Int. 23(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  11^th 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  2^nd 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  12^th 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. 12^th Aust. Wine Ind. Tech. Conf. July, 2004, Melbourne. p 290.

  2007  23^rd 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  23^rd 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  23^rd 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 23^rd 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 13^th 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  13^th 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  13^th 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  13^th 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  24^th 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  24^th 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  24^th 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  4^th Australian conference on Yeast: Products and Discovery (Adelaide)

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

  2009  4^th 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  14^th 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   15^th 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   15^th 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   15^th 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   15^th 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   15^th 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   14^th 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)

Entry last updated: Saturday, 13 Feb 2021