Sterilization of Escherichia coli cells by the application of pulsed magnetic field.

The inactivation of microorganisms by pulsed magnetic field was studied. It was improved that the application of electromagnetic pulses evidently causes a lethal effect on E. coli cells suspended in phosphate buffer solution Na2HPO4/NaH2PO4 (0.334/0.867 mmol/L). Experimental results indicated that the survivability (N/N0; where N0 and N are the number of cells survived per milliliter before and after electromagnetic pulses application, respectively) of E. coli decreased with magnetic field intensity B and treatment time t. It was also found that the medium temperatures, the frequencies of pulse f, and the initial bacterial cell concentrations have determinate influences in destruction of E. coli cells by the application of magnetic pulses. The application of an magnetic intensity B = 160 mT at pulses frequency f= 62 kHz and treatment time t = 16 h result in a considerable destruction levels of E. coli cells (N/N0 = 10(-4)). Possible mechanisms involved in sterilization of the magnetic field treatment were discussed. In order to shorten the treatment time, many groups of parallel inductive coil were used. The practicability test showed that the treatment time was shortened to 4 h with the application of three groups of parallel coil when the survivability of E. coli cells was less than 0.01%; and the power consumption was about 0.2 kWh/m3.