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Formulations for Freeze-drying of Bacteria and Their Influence on Cell Survival
08:55

Formulations for Freeze-drying of Bacteria and Their Influence on Cell Survival

Published on: August 3, 2013

Influence of freeze-drying conditions on survival of Oenococcus oeni for malolactic fermentation

Guoqun Zhao1, Gui Zhang

  • 1Hebei University of Science and Technology, Shijiazhuang, 050018, China. gqzhao18@126.com

International Journal of Food Microbiology
|August 22, 2009
PubMed

Insights

Optimizing freeze-dried Oenococcus oeni starter cultures for malolactic fermentation involves specific preparation steps. Cell washing, a neutral pH suspension medium, preincubation, and controlled freezing temperatures significantly enhance bacterial viability for winemaking.

Area of Science:

  • Enology
  • Microbiology
  • Food Science

Background:

  • Malolactic fermentation (MLF) is crucial for wine quality, primarily driven by Oenococcus oeni.
  • Starter culture technology using O. oeni aims to reliably induce MLF in wine production.
  • Preservation of O. oeni viability in freeze-dried starter cultures is essential for consistent fermentation.

Purpose of the Study:

  • To investigate factors affecting the viability of freeze-dried Oenococcus oeni H-2.
  • To optimize conditions for preserving O. oeni during the freeze-drying process for starter culture applications.

Main Methods:

  • Evaluating the impact of cell washing with potassium phosphate buffer on cell viability.
  • Assessing the effect of suspension medium pH on O. oeni survival.
  • Determining the influence of preincubation temperature and sodium glutamate concentration on viability.
  • Analyzing the effect of initial cell concentration and various freezing temperatures on freeze-dried O. oeni.

Main Results:

  • Cell washing significantly improved viability compared to unwashed samples.
  • Optimal cell survival was observed at a suspension medium pH of 7.0.
  • Preincubation at 25°C enhanced cell viability before freezing.
  • An initial cell concentration of 10^9 CFU/ml was optimal with 2.5% sodium glutamate.
  • Viability increased with decreasing freezing temperatures from -20°C to -65°C, but decreased significantly at -196°C (liquid nitrogen).

Conclusions:

  • Specific pre-treatment and cryopreservation parameters are critical for maximizing O. oeni viability in freeze-dried starter cultures.
  • Optimized methods ensure a more robust and reliable O. oeni inoculum for successful malolactic fermentation in winemaking.
  • Further research into cryoprotective agents and freezing protocols can improve the shelf-life and efficacy of O. oeni starter cultures.

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