The survival of three kinds of microorganisms under strongpulse electric field conditions was investigated with a possible application of the electric pulse method for sterilization of consumable liquids. The results of the investigations of survival ratio of Gram-negative (Escherichia coli, Yersinia enterocolitica) and Gram-positive (Staphylococcus aureus, Listeria monocytogenes) bacteria and yeastlike fungi (Candida albicans) are presented. The HV pulses with peak voltage U = 0 to 100 kV and rise time t , = 0.5 to 1.2 ps were applied. The microorganisms were suspended in an NaCl solution with 7 = 6 t o 13 mS/cm conductivity and pH = 7.2. The experimental setup and the dependency of the microorganism survival ratio on the rise time, peak voltage and on the number of pulses applied, are presented. It has been found that the lethal effect on microorganisms caused by HV pulses depends on the pulse parameters as well as on the kind of microorganism being treated.

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Electron beam irradiations of aqueous solutions containing 15-30 mg/L of nitrobenzene at 60 kGy dose removed 78% of the contaminant. Three mononitrophenols were detected as by-products of electron beam treatment of nitrobenzene. A mixed culture enriched on a mixture of 2-, 3-, and 4-nitrophenol degraded both the residual nitrobenzene and the nitrophenol products. Percentage removal of nitrobenzene increased with increasing electron beam dose. This observation led to the conceptual design of a two-stage electron beam microbial process for degradation of nitrobenzene. Three groups of pure isolates were characterized from the mixed culture based on their abilities to grow on cor- responding nitrophenol substrates: Group A, 2NP(-)3NP(-)4NP(+); Group B, 2NP(+)3NP(+)4NP(-); and Group C, 2NP(-)3NP(+)4NP(-). Bacteria that grew on 3-NP transformed nitrobenzene into ammonia in the electron beam-treated nitrobenzene samples.

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