Interaction of sub-microsecond pulsed electric field with bacterial cells

In the bacterial decontamination of liquid foods, the use of a sub microsecond pulsed electric field is of significant interest because it offers advantages such as negligible thermal effects, superior energy efficiency, and a much-reduced probability of medium breakdown. The reduced pulse duration also affects the mechanism by which sub microsecond pulses inactivate bacterial cells. We provide insight into possible bacterial inactivation mechanisms by sub-microsecond electric pulse with the aid of a common bacterium-wild type Escherichia coli and its mutants. Two pulsed power sources have been designed, developed and tested-one with pulse duration of 32 ns, the other 700 ns, and both are capable of establishing sufficiently high electric field intensity. The experimental results suggest that bacterial inactivation by 700 ns pulses is due to electrical breakdown of the outer cell membrane, whereas inactivation by 32 ns pulses is possibly due to interaction with intracellular structures.