Michelle E. Walker
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View article: Genomic analysis of Kazachstania aerobia and Kazachstania servazzii reveals duplication of genes related to acetate ester production
Genomic analysis of Kazachstania aerobia and Kazachstania servazzii reveals duplication of genes related to acetate ester production Open
Kazachstania aerobia and Kazachstania servazzii can affect wine aroma by increasing acetate ester concentrations, most remarkably phenylethyl acetate and isoamyl acetate. The genetic basis of this is unknown, there being little to no seque…
View article: Modern yeast development: finding the balance between tradition and innovation in contemporary winemaking
Modern yeast development: finding the balance between tradition and innovation in contemporary winemaking Open
A key driver of quality in wines is the microbial population that undertakes fermentation of grape must. Winemakers can utilise both indigenous and purposefully inoculated yeasts to undertake alcoholic fermentation, imparting wines with ar…
View article: Characterization of polysulfides in Saccharomyces cerevisiae cells and finished wine from a cysteine-supplemented model grape medium
Characterization of polysulfides in Saccharomyces cerevisiae cells and finished wine from a cysteine-supplemented model grape medium Open
Polysulfide degradation in wine can result in hydrogen sulfide (H2S) release, imparting a rotten-egg smell that is detrimental to wine quality. Although the presence of wine polysulfides has been demonstrated, their biogenesis remains uncl…
View article: Effect of ‘loss of function’ mutation in <i> SER1 </i> in wine yeast: fermentation outcomes in co-inoculation with non-<i>Saccharomyces </i>
Effect of ‘loss of function’ mutation in <i> SER1 </i> in wine yeast: fermentation outcomes in co-inoculation with non-<i>Saccharomyces </i> Open
In wine fermentation, improved wine complexity and sensorial properties can arise from the use of non-Saccharomyces yeast. Generally less alcohol tolerant, such strains often do not finish fermentation, therefore requiring a second inocula…
View article: Directed evolution as an approach to increase fructose utilization in synthetic grape juice by wine yeast AWRI 796
Directed evolution as an approach to increase fructose utilization in synthetic grape juice by wine yeast AWRI 796 Open
In winemaking, slow or stuck alcoholic fermentation can impact processing efficiency and wine quality. Residual fructose in the later stages of fermentation can leave the wine ‘out of specification’ unless removed, which requires reinocula…
View article: The effect of grape juice dilution and complex nutrient addition on oenological fermentation and wine chemical composition
The effect of grape juice dilution and complex nutrient addition on oenological fermentation and wine chemical composition Open
The impact of water addition and complex nutrient addition to grape juice in laboratory scale winemaking, on both alcoholic and malolactic fermentation duration and outcome has been examined using commercial wine yeasts, Lalvin EC1118™ and…
View article: ‘TeeBot’: A High Throughput Robotic Fermentation and Sampling System
‘TeeBot’: A High Throughput Robotic Fermentation and Sampling System Open
When fermentation research requires the comparison of many strains or conditions, the major bottleneck is a technical one. Microplate approaches are not able to produce representative fermentative performance due to their inability to trul…
View article: Disruption of<i>ECM33</i>in diploid wine yeast EC1118: cell morphology and aggregation and their influence on fermentation performance
Disruption of<i>ECM33</i>in diploid wine yeast EC1118: cell morphology and aggregation and their influence on fermentation performance Open
When investigating yeast gene function in relation to fermentation, many screens rely on haploid yeast derivatives. This, however, is not representative of industrial strains, which are typically diploid. One such example is the disruption…
View article: The effect of grape juice dilution on oenological fermentation
The effect of grape juice dilution on oenological fermentation Open
The impact of water addition to grape juice in winemaking, on both alcoholic and malolactic fermentation duration and outcome has been examined using commercial wine yeasts, Lalvin EC1118™ and Lalvin R2™ and malolactic bacteria Lalvin VP41…
View article: Brief temperature extremes during wine fermentation: effect on yeast viability and fermentation progress
Brief temperature extremes during wine fermentation: effect on yeast viability and fermentation progress Open
Background and Aims: The impact on viability and metabolic activity of rapid, short-term exposure of yeast cells to markedly variable temperature is largely unexplored. Fermentation mass loss, flow cytometry using propidium iodide and FUN-…
View article: Use of a wine yeast deletion collection reveals genes that influence fermentation performance under low-nitrogen conditions
Use of a wine yeast deletion collection reveals genes that influence fermentation performance under low-nitrogen conditions Open
A deficiency of nitrogenous nutrients in grape juice can cause stuck and sluggish alcoholic fermentation, which has long been a problem in winemaking. Nitrogen requirements vary between wine yeast strains, and the ability of yeast to assim…
View article: Yeast genes involved in regulating cysteine uptake affect production of hydrogen sulfide from cysteine during fermentation
Yeast genes involved in regulating cysteine uptake affect production of hydrogen sulfide from cysteine during fermentation Open
An early burst of hydrogen sulfide (H2S) produced by Saccharomyces cerevisiae during fermentation could increase varietal thiols and therefore enhance desirable tropical aromas in varieties such as Sauvignon Blanc. Here we attempted to ide…
View article: The yeast TUM1 affects production of hydrogen sulfide from cysteine treatment during fermentation
The yeast TUM1 affects production of hydrogen sulfide from cysteine treatment during fermentation Open
The undesirable rotten-egg odour of hydrogen sulfide (H2S) produced by yeast shortly after yeast inoculation of grape musts might be an important source of desirable varietal thiols, which contribute to tropical aromas in varieties such as…