Osmotic tolerance response of biocontrol agent Yarrowia lipolytica m18/3b under pre- and postharvest conditions

A pre-adaptation approach to osmotic stress was used to improve the colonisation and biocontrol capacity of Yarrowia lipolytica M18/3b on the apple under pre- and postharvest conditions. For this, M18/3b strain was cultured in an unmodified NYDB medium (0.996a (w)) or in different media with water stress (0.950-0.970a (w)) produced by the addition of NaCl, sorbitol, or glycerol and the impact on the growth rate in them was evaluated. Furthermore, the population dynamic of the yeast was evaluated on the apple surface under field and storage conditions. Treated fruits were also inoculated with Penicillium expansum and the disease incidence and severity were measured. Finally, the content of intracellular sugars and polyols on pre-adapted M18/3b cells was determined. The results showed that development of the M18/3b strain in the modified media was affected by the solute used to reduce the a (w). The cells adapted with glycerol (0.960a (w)) reached higher population levels on the apple surface, both in pre- and postharvest conditions. Furthermore, an increase in the antagonistic activity of M18/3b pre-adapted with glycerol was obtained in the field application. In contrast, pre-adaptation with sorbitol had adverse effects on the colonisation capacity of the antagonist. Additionally, pre-adapted cells with NaCl and sorbitol showed an accumulation of erythritol and a significant decrease of trehalose compared with non-adapted cells. In conclusion, the osmotic treatment with glycerol at 0.960a (w) increased the survival of Y. lipolytica M18/3b cells on the fruit surface and enhanced the antagonistic activity to control blue mould when apples were treated in pre-harvest.

Automated summary

A pre-adaptation approach to osmotic stress, specifically using glycerol treatment, can enhance the colonization and biocontrol capacity of Yarrowia lipolytica M18/3b on apples under field and storage conditions. The adaptation with glycerol led to higher population levels on the apple surface and increased antagonistic activity, while adaptation with sorbitol had adverse effects on colonization capacity. Cells pre-adapted with NaCl and sorbitol showed changes in intracellular sugars and polyols compared to non-adapted cells.