CO2-driven changes in energy and fermentative metabolism in harvested strawberries

Short postharvest exposure of strawberries to high CO2 levels provides significant benefits in reducing decay and controlling physiological disorders during storage at 0 °C. To define the different strategies employed by strawberries to tolerate high CO2 concentrations, the impact of different CO2 concentrations on energy and fermentative metabolism was studied under the same conditions of O2 availability. Our data indicate that metabolic depression represents a strategy to effectively adapt to beneficial high CO2 concentrations, with a decrease in ATP levels and in the energy charge, along with moderate ethanolic fermentation. Moreover, the induction of fermentative genes does not appear to be essential for the accumulation of fermentative metabolites. By contrast, when fruit is stored in air without added CO2, the metabolism is not directed towards fermentation and is accompanied by a high ATP/ADP ratio and energy charge. However, when exposed to 40 kPa CO2, the excessively low energy charge and excessive decrease in ATP could not match the ATP requirements, in a process that ultimately causes significant perturbations including a high lipid peroxidation.