Poster Presentation Australian Microbial Ecology 2022

Carbohydrate assimilation profiles and enzyme secretion of Kazachstania yeasts (#154)

Anna Wittwer 1
  1. School of Agricultural, Food, and Ecosystem Sciences, The University of Melbourne, Melbourne

Food fermentations are populated by defined and generally stable microbial communities [1]. The sourdough starters with which sourdough bread is made are typically refreshed daily and contain bacteria and yeasts [2]. These starters often contain yeasts from the genus Kazachstania, however little is known about the genetic or metabolic capabilities of these common sourdough yeasts [3,4]. The substrate of these yeasts, flour dough, has a well-defined composition. It is mainly composed of starch, and also contains smaller oligo-, di-, monosaccharides and polyols [5]. The mechanisms by which sourdough yeasts degrade these carbohydrates may play a role in maintaining the microbial diversity of distinct yeast populations. Here I describe carbohydrate utilisation assays in a collection of 23 Kazachstania isolates from a range of different species sourced from sourdoughs in Victorian bakeries, isolated from wheat and in culture collections. Isolates that demonstrated promising assimilation profiles in agar surface-based assays were further investigated in liquid media, and with a Durham-tube based assay of fermentation. The subcellular location of enzymes involved in these properties were also investigated. The results of this study will be carried into further work which uses carbohydrate degradation as a means of maintaining microbial communities in sourdough and as the basis of nutrient exchange with other community members, including bacteria.

  1. Oshiro, M. et al. (2021) Mechanistic Insight into Yeast Bloom in a Lactic Acid Bacteria Relaying-Community in the Start of Sourdough Microbiota Evolution. Microbiol. Spectr. 9, e00662-21
  2. Van Kerrebroeck, S. et al. (2017) Sourdoughs as a function of their species diversity and process conditions, a meta-analysis. Trends Food Sci. Technol. 68, 152–159
  3. Arora, K. et al. (2021) Thirty years of knowledge on sourdough fermentation: A systematic review. Trends Food Sci. Technol. 108, 71–83
  4. Devillers, H. et al. (2022) Whole-Genome Sequences of Two Kazachstania barnettii Strains Isolated from Anthropic Environments. Genome Biol. Evol. 14, 1–6
  5. Food Standards Australia New Zealand Jan-(2022) , Australian Food Composition Database. . [Online]. Available: https://www.foodstandards.gov.au/science/monitoringnutrients/afcd/Pages/default.aspx