Bacterial sterilization and intracellular protein release by a pulsed electric field.

Several biotechnological applications of high-voltage pulsed electric field (PEF) are introduced. Electrical breakdown or disruption of a biological membrane by PEF is understood to occur by electromechanical compression, which results in the formation of transmembrane pores. If the total area of induced pores is small in relation to the total surface area of the membrane, the pores are able to close again mainly through the diffusion of the lipid molecules and rearrangement of the proteins (reversible disruption). If the total area of the pores becomes unfavorably large, the membrane is no longer able to repair these perturbations (irreversible disruption), and that results in sterilization. We have investigated effective sterilization by using PEF-induced irreversible disruption of biological membranes. The treatment temperature or growth temperature was found to have a great effect on PEF sterilization. The shape of the treatment chamber also proved important for effective PEF sterilization. Therefore, a number of reactors having novel structures were developed. We have also verified that this PEF-induced reversible disruption could be utilized for the selective release of intracellular proteins from yeast and certain gene-engineered Escherichia coli. The secretion of periplasmic protein from E. coli was achieved during cultivation.