Electric and Magnetic Fields in Microbial Biotechnology: Possibilities, Limitations, and Perspectives

Abstract

This paper is designed to provide an introduction to the major directions in the use of electromagnetic fields (EMFs) of various types, amplitudes, frequencies, waveforms, and treatment times in microbial biotechnology. An attempt is made to compare critically some recently reported results and to outline the most promising areas for future research. Theory is mentioned when necessary, but the main emphasis has been placed on practical applications. Selected examples of relevance to biotechnology are discussed with respect to their advantages and drawbacks compared with conventional methods. The main advantage of the strong electric field pulse techniques such as electroporation and electrofusion is that, in many cases, they are more easily controlled and more effective than the classic techniques. If cell inactivation is desired, non-thermal killing by strong pulses or fast thermal sterilization by means of ohmic heating can be achieved. However, if cell viability must be preserved, problems such as adverse effects of toxic electrolytic products or a significant medium temperature increase can arise. Constant and pulsing magnetic fields and direct and alternating electric currents might be applied to regulate (stimulate or inhibit) cell proliferation or monitor cell growth and various other metabolic activities. A number of specific cell-independent factors can act synergistically with an external EMF, thus strongly modifying its effect. Therefore, highly efficient integrated processes such as polymer-tDedicated to Hermann Berg, a pioneer in bioelectrochemistry, on the occasion of his 75th birthday. 186VELIZAROV supported electrofusion, electrodialysis culture, and bioelectrochemical conversions could be successfully operated. However, especially if large-scale processes are considered, economic reasons, scale-up difficulties, and subjective factors still limit a wider application of EMFs. The design of more efficient and cost-effective exposure conditions and the development of novel integrated bioelectro-processes are the major challenges in increasing the use and benefit of EMFs in biotechnology.

Characterization of a stirred tank electrochemical cell for water disinfection processes

“…In particular, an increase of the current density results in a more effective inactivation of bacteria, due to the greater amount of OX which may be present in the liquid bulk. As in the batch experiments the bulk reaction 10 10,000 N.D. 10 1,500 N.D. 5 10,000 0.26 Initial suspension composition: E. coli 1 × 10 3 CFU/ml, coliforms 3 × 10 3 CFU/ml, enterococci 3 × 10 4 CFU/ml in Na 2 SO 4 1 mM.…”

“…Methods based on UV irradiation techniques and TiO 2 photocatalyzed processes [6,7] were also proposed. Electrochemical disinfection by direct electrolysis demonstrated to be effective in killing a wide spectrum of microorganisms [8][9][10][11]. Nevertheless, although experimental studies were carried out in this field, large scale applications in the water treatment are still not present, electrochemical reactors being only utilised to produce chlorine or ozone, which constitute the effective disinfectants.…”

Modification of bacterial cellulose through exposure to the rotating magnetic field

“…The application of different types of magnetic fields (MFs) is a novel engineering approach that may be used during BC biosynthesis process (Velizarov, 1999). The studies on the use of MFs in the biotechnological process conducted to date have concerned mostly static magnetic fields (SMFs), whereas the biotechnologically promising idea to use rotating magnetic fields (RMFs) still remains unexplored (Hristov, 2010).…”

Effect of electrokinetic transport on the vulnerability of PAH-degrading bacteria in a model aquifer

“…the indigenous HOC-degrading soil bacteria ). When DC is applied to living microbial cells, various responses, such as toxic electrode effects, metabolic stimulation due to enhanced substrate mass transfer (Pribyl et al 2001), sublethal injuries (Guillou et al 2003), irreversible dielectric cell membrane breakdown (Zimmermann et al 1974), or changes in the physicochemical surface properties (Luo et al 2005) can be observed depending on the applied current, treatment time, cell type and medium characteristics (Velizarov 1999). Earlier studies using soil have shown that the application of 20 mA cm -2 DC current stimulated the activity of sulphur-oxidising bacteria (Jackman et al 1999) or the biological denitrification of nitrate-contaminated groundwater (Hayes et al 1998) due to the production of H 2 and subsequent pH changes.…”