Electroporation-assisted inactivation of Escherichia coli using nisin-loaded pectin nanoparticles

Pulsed electric fields (PEF) trigger the electroporation phenomenon in cell membranes, which has found many biotechnological applications including food processing. Nisin is a prominent lantibiotic widely used as a food preservative due to its high potency against many bacteria; its efficacy depends on various environmental factors and nisin resistance is a common problem. In this work we have applied novel nisin-loaded pectin nanoparticles in combination with sub-microsecond and microsecond range electroporation for inactivation of nisin-resistant Escherichia coli. The 5–30kVcm−1 square wave 1kHz pulse bursts of 250ns, 500ns, and 100μs were used. The PEF treatment combined with nisin nanoparticles further improved the inactivation efficacy (up to 3.7 log reduction) compared to separate procedures (up to 1.5 log reduction); this effect is scalable and does not depend on the cell concentration.We have designed experiments and provided data that has direct application in food preservation and processing. Nisin is a prominent lantibiotic that is widely used as a food preservative due to its high potency against many bacteria. Nevertheless, its efficacy depends on various environmental factors and the nisin resistance is a common problem. We have used the pectin encapsulation that allowed addressing the susceptibility of nisin to environmental factors such as pH or food composition, while the PEF technology enabled a non-thermal increase of the membrane permeabilization and overcoming the nisin-resistance of the bacteria. We have also shown that the only reason to use submicrosecond pulses instead of the microsecond ones for eradication of the bacteria is the possible minimization of energy costs for generation of PEF. If the total energy of the pulse burst is the same the inactivation efficacy is also identical.