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Predicted ecological niches and environmental resilience of different formulations of the biocontrol yeast Candida sake CPA-1 using the Bioscreen C

Carbó, A., Torres, R., Teixidó, N., Usall, J., Magan, N., Medina, A.
BioControl 2018 v.63 no.6 pp. 855-866
Botrytis cinerea, Candida sake, Penicillium expansum, Rhizopus stolonifer, absorbance, automation, biological control, biological control agents, environmental factors, grape juice, growth curves, niches, pH, potato starch, rapid methods, temperature, water activity, yeasts
Environmental resilience of biocontrol microorganisms has been a major bottleneck in the development of effective formulations. Candida sake is an effective biocontrol agent (BCA) against Penicillium expansum, Botrytis cinerea or Rhizopus stolonifer, and different formulations of the BCA have been optimised recently. The objective of this study was to compare the relative tolerance of different dry and liquid formulations of the biocontrol yeast C. sake CPA-1 to interacting environmental conditions using the Bioscreen C. Initially, the use of this automated turbidimetric method was optimised for use with different formulations of the biocontrol yeast. The best growth curves were obtained for the C. sake CPA-1 strain when grown in a synthetic grape juice medium under continuous shaking and with an initial concentration of 10⁵ CFUs ml⁻¹. All the formulations showed a direct relationship between optical density values and yeast concentrations. Temperature (15–30 °C) and water activity (aw; 0.94–0.99) influenced the yeast resilience most profoundly, whereas the effect of pH (3–7) was minimal. In general, the liquid formulation grew faster in more interacting environmental conditions but only the yeast cells in the dry potato starch formulation could grow in some stress conditions. This rapid screening method can be used for effective identification of the resilience of different biocontrol formulations under interacting ecological abiotic conditions.