Pulsed electric field (PEF) can induce irreversible electroporation in the bio-membrane and cause the death of microbial cells without significant thermal effect, which can be used for inactivation of microorganisms and facilitation lysis of microbial cells for lipid extraction. The present study aimed to investigate the efficiency of PEF treatment of Arthrospira platensis and Saccharomyces cerevisiae using test cells with different types of electrodes and impulses with different waveshapes. An equivalent circuit modelling approach was also proposed and developed to describe the pulsed power system and the microbiological cell in the present study.The PEF test cells with three types of electrodes were developed in the present study: a traditional stainless steel test cell; a novel low-conductive test cell with 2 μm TiO2-coating on electrode surface; and a novel test cell with non-conductive ceramic electrodes. Effective PEF inactivation of both A. platensis and S. cerevisiae was achieved using stainless steel and TiO2-coated test cells. Significant improvement in the energy efficacy of the PEF treatment was obtained using the TiO2-coated test cell. However, PEF inactivation of microorganisms in the ceramic test cell required electric fields with magnitude above 80 kV/cm.Three types of impulses, square impulse, smooth exponential impulse and oscillating exponential impulse were used in the present study. The best energy efficacy was achieved using the smooth exponential impulse for the field levels of 67 kV/cm and 80 kV/cm. A correlation between the pulse waveshape, the electric field magnitude and the inactivation performance was established.The PEF treatments of A. platensis demonstrated that this type of cyanobacteria can be inactivated effectively but rupture of the cell structure was not achieved.The PEF process was capable of induction of the lethal damage to the A. platensis cells but not sufficient to cause significant mechanical damage to the cell structure.
|Date of Award||17 Oct 2016|
- University Of Strathclyde
|Sponsors||University of Strathclyde|
|Supervisor||Igor Timoshkin (Supervisor) & Scott MacGregor (Supervisor)|