Application of surface-active substances produced by Rhodococcus erythropolis IMB Aс-5017 for post-harvest treatment of sweet cherry

Abstract

Introduction. The aim of the present study was testing of the supernatant of Rhodococcus erythropolis ІМВ Ас-5017 with different concentration of surface-active substances (SAS) for treatment of sweet cherry for shelf-life extension. Materials and methods. R. erythropolis ІМВ Ас-5017 were grown in the medium with ethanol. Supernatant with concentration of SAS from 0.1 to 0.5 g/L was used for the treatment of sweet cherry fruit. Concentration of SAS in supernatant was determined by weight method. The total number of heterotrophic bacteria and fungi were determined by the plate dilution method. Results and discussion. The treatment of sweet cherries with a supernatant containing 0.5 g/L SAS diminished the numbers of bacteria and fungi on the fruit’s surface by 10 and 5 times, respectively, in comparison with cherries washed with water. The treatment of sweet cherries with supernatant containing 0.2 g/L SAS diminished the numbers of bacteria and fungi on the fruit’s surface by 5 and 3 times, respectively; treatment with supernatant containing 0.1 g/L diminished the numbers of bacteria and fungi by 2 times in comparison with cherries washed with water. The treatment with supernatant with concentration SAS 0.5 g/L was most effective. Treated with supernatant sweet cherries fruits did not show signs of decay even on 7th day of storage, while untreated or washed with water fruits lost moisture, fruit’s skin became wrinkled, cracks and decayed areas appeared on it. Content of fungal cells on the surface of sweet cherry pretreated with supernatant with concentration of SAS from 0.1 to 0.5 g/L and after that contaminated with spore’s suspension of Aspergillus niger Р-3 were by 2 – 11 times lower than on the surface of fruits washed with water after 5 days of incubation. The possibility of multiple usage of supernatant was shown. Application of supernatant with concentration of 0.5 g/L resulted in decrease of bacterial concentration after first usage by 10 times, after second usage it was diminished by 5 times and after third usage it was diminished by 3 times, meanwhile concentration of fungi decreased by 9, 5 and 4 times after I, II, and III usage of supernatant. Conclusion. Surface-active substances synthesized by Rhodococcus erythropolis IMB Ac-5017 could be used for treatment of sweet cherry to extend their shelf life.