Improved Antimicrobial Activity through Synergistic Action of Microparticulate Chitosan and Short Sustained Electric Field

Techniques to inhibit gram-negative bacteria such as shiga-toxin producing Escherichia coli are valuable as the prevalence of large-scale industrial food preparation increases the likelihood of contamination. Chitosan, the deacetylated derivative of chitin, has been demonstrated to inhibit bacteria growth in acidic environments, but is significantly less effective in preventing bacteria grown at pH > 7.0. Pulsed electric fields, constituting another method of bacteria inhibition, are difficult to generate at sufficient strength due to the high electric potentials required. It is therefore of interest to combine the charge-dependent nature of the two techniques to allow for increased inhibition of gram-negative bacteria. Chitosan microparticles are demonstrated to flocculate E. coli, inhibit growth, and increase in efficacy when combined with a low voltage electric field applied over various short time periods. Using short sustained pulses of approximately 100 V/cm it is demonstrated that bacteria viability is reduced by several orders of magnitude. This effect is increased when chitosan microparticles are introduced to the system prior to electroporation.