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Influence of plasma and plasma activated water on fungi Aspergillus niger
Žitný, Michal ; Čechová, Ludmila (referee) ; Kozáková, Zdenka (advisor)
The thesis deals with the issue of decontamination of Aspergillus niger mold using plasma, plasma-activated water and their combination. The theoretical part concerns the effects on the general properties of plasma, its generation, effects on microorganisms known so far and its use in industry with a special focus on medicine. It also focuses on the generation and characterization of plasma-activated water, its effects on bacteria, yeasts and fungi and its use. It also deals with the description of fungi, their occurrence and their sterilization. Part of the theory was aimed directly at the fungus Aspergillus niger. Its cultivation and its industrial uses, such as its use for the cultivation of citric acid, were described here. The experimental part deals with the characterization of plasma-activated water generated using a torch jet. The influence of the supplied power on the formation of particles in plasma-activated water was monitored. The decontamination effect of the plasma, generated by the torch jet, alone and in combination with plasma-activated water generated by alternating and direct current is monitored. The characterization of plasma activated water was performed with 20 ml of distilled water at a carrier gas rate of 2 l/min and a power of a microwave source of 9 and 12 W. The decontamination effect of plasma and its combination with plasma-activated water was observed by inoculating 100 l of a ten-fold and a hundred-fold diluted treated mold culture on Petri dishes with malt agar. The evaluation of the effect was carried out by counting the grown fungal colonies and subsequent comparison with control samples. All measured and obtained data were processed in the results. Plasma activated water generated by the torch jet has been found to contain higher concentrations of nitrogenous substances and lower concentrations of hydrogen peroxide, with the generated nitrate concentrations being higher at lower output than at higher output. DC-generated plasma activated water containing low concentrations of nitrogenous species and a very high concentration of hydrogen peroxide compared to PAW generated by a torch jet. Furthermore, plasma-activated water generated using a high frequency source contains minimal concentrations of nitrogenous substances and slightly elevated concentration of hydrogen peroxide in regard to torch jet PAW. The highest decontamination effect of all the methods used was the combination of plasma and plasma activated water, prepared by a plasma nozzle using direct voltage, when the plasma was applied first. On the contrary, the least effective method was the application of plasma and plasma activated water, generated by high frequency voltage. Limiting oxygen access had almost no effect on direct plasma treatment, but other methods were significantly affected by it. The greatest difference in decontamination effect was observed for the combination of plasma and plasma activated water, generated by high frequency current, where the difference was up to 30 %, but all methods had a significant decontamination effect compared to the control.
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Influence of plasma and plasma activated water on fungi Aspergillus niger
Žitný, Michal ; Čechová, Ludmila (referee) ; Kozáková, Zdenka (advisor)
The thesis deals with the issue of decontamination of Aspergillus niger mold using plasma, plasma-activated water and their combination. The theoretical part concerns the effects on the general properties of plasma, its generation, effects on microorganisms known so far and its use in industry with a special focus on medicine. It also focuses on the generation and characterization of plasma-activated water, its effects on bacteria, yeasts and fungi and its use. It also deals with the description of fungi, their occurrence and their sterilization. Part of the theory was aimed directly at the fungus Aspergillus niger. Its cultivation and its industrial uses, such as its use for the cultivation of citric acid, were described here. The experimental part deals with the characterization of plasma-activated water generated using a torch jet. The influence of the supplied power on the formation of particles in plasma-activated water was monitored. The decontamination effect of the plasma, generated by the torch jet, alone and in combination with plasma-activated water generated by alternating and direct current is monitored. The characterization of plasma activated water was performed with 20 ml of distilled water at a carrier gas rate of 2 l/min and a power of a microwave source of 9 and 12 W. The decontamination effect of plasma and its combination with plasma-activated water was observed by inoculating 100 l of a ten-fold and a hundred-fold diluted treated mold culture on Petri dishes with malt agar. The evaluation of the effect was carried out by counting the grown fungal colonies and subsequent comparison with control samples. All measured and obtained data were processed in the results. Plasma activated water generated by the torch jet has been found to contain higher concentrations of nitrogenous substances and lower concentrations of hydrogen peroxide, with the generated nitrate concentrations being higher at lower output than at higher output. DC-generated plasma activated water containing low concentrations of nitrogenous species and a very high concentration of hydrogen peroxide compared to PAW generated by a torch jet. Furthermore, plasma-activated water generated using a high frequency source contains minimal concentrations of nitrogenous substances and slightly elevated concentration of hydrogen peroxide in regard to torch jet PAW. The highest decontamination effect of all the methods used was the combination of plasma and plasma activated water, prepared by a plasma nozzle using direct voltage, when the plasma was applied first. On the contrary, the least effective method was the application of plasma and plasma activated water, generated by high frequency voltage. Limiting oxygen access had almost no effect on direct plasma treatment, but other methods were significantly affected by it. The greatest difference in decontamination effect was observed for the combination of plasma and plasma activated water, generated by high frequency current, where the difference was up to 30 %, but all methods had a significant decontamination effect compared to the control.
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