Decontamination of Escherichia coli biofilm on polystrene surface by application of organic acid and thermosonication

In this study, it was aimed to inactivate Escherichia coli biofilms on the food contact surface by the treatments of organic acid and sonication. Polystyrene microplates were used as food contact surfaces and E. coli biofilms were grown on these plates. Plates containing E. coli biofilm were exposed to sonication with different inactivation solutions (PBS, lactic acid and acetic acid) at different temperatures (20, 40 and 50oC) and times (2 and 5 minutes). The effects of temperature, time and inactivation solution on E. coli biofilm inactivation were found to be statistically significant (p<0.05). With the sonication treatment under different conditions, viable cell count of the E. coli biofilm was decreased by 0.43-6.21 log cfu/mL and its optical density (OD600) was decreased by 0.13-0.72. The highest E. coli biofilm inactivation was achieved by organic acid and ultrasonication at 50oC for 5 minutes. It was found that there was a significantly positive correlation between test methods based on viable cell count and optical density measurement in E. coli biofilm inactivation. According to multiple linear regression analysis, independent variables such as temperature, time and solution explained 94% and 80% of the change in E. coli biofilm inactivation based on viable cell count and optical density measurement, respectively. As a result, test methods based on live cell counting were found to be more reliable in inactivation experiments. Additionally, organic acid and thermosonication treatment have been suggested for effective sanitation of food industry contact surfaces.