Effects of Atmospheric Pressure Dielectric Barrier Discharge Plasma Irradiation on Yeast Growth
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Effects of Atmospheric Pressure Dielectric Barrier Discharge Plasma Irradiation on Yeast Growth Satoshi Kitazaki1, Kazunori Koga1, Masaharu Shiratani1, and Nobuya Hayashi2 1 Graduate School of Information Science and Electrical Engineering, Kyushu University, 744 Motooka, Nishi-ku, Fukuoka, 819-0395, Japan 2 Interdisciplinary Graduate School of Engineering Sciences, Kyushu University, 6-1 Kasugakoen, Kasuga-shi, Fukuoka 816-8580, Japan ABSTRACT We investigated effects of atmospheric pressure dielectric barrier discharge (DBD) plasma irradiation on growth characteristics of bread yeast (Saccharomyces cerevisie). Nitric oxide of 400 ppm and O3 above 200 ppm are produce by the DBD plasmas. DBD plasma irradiation of 50 and 100 s enhances the growth of yeast in the lag phase, whereas 150 s irradiation suppresses the growth. There is an optimum duration of plasma irradiation for the growth promotion. INTRODUCTION Nonthermal atmospheric pressure plasmas have been employed for biomedical processing applications, because they provide high density radicals at a low gas temperature [18]. Recently nonthermal atmospheric pressure plasmas as well as low pressure plasmas have been employed for growth promotion of human cells [9] and plants [10-20]. For example, torch type plasmas and microwave plasmas are used for wheat and oat germination. Pulse power discharge has been studied for promotion of mushrooms. Such enhancement of cell proliferation by plasma irradiation is useful in many fields of cancer therapy, regenerative medicine, fermentation industry, and so on. Final goal of our study is to regulate cell proliferation using plasma irradiation. Here we have developed a scalable atmospheric pressure dielectric barrier discharge (DBD) device for biomedical processing in a large area and have employed the device to growth control of bread yeast for fermentation applications. EXPERIMENTAL Figure 1 shows a schematic of the DBD discharge device. The device consisted of 20 electrodes of a stainless rod of 1 mm in outer diameter and 60 mm in length covered with a ceramic tube of 2 mm in outer diameter. They were arranged alternately in equal intervals (0.2mm). When AC high voltage power was supplied to the electrodes using a high voltage power supply (Logy Electric, LHV-09K), DBD was generated uniformly between electrodes. The discharge region was 1400 mm2. The instantaneous waveforms of the discharge voltage and the discharge current were measured using a high-voltage probe (Tektronix, P6015A) and a Rogowski coil (YOKOHAMA, CTL-28-S90-05Z-1R1), respectively. Optical emission spectra from the discharge plasmas were measured with a spectrometer (Ocean Optics, USB2000) to obtain information on radicals generated by the DBD plasmas. We also measured gas
concentration of nitric oxide and O3 generated by the discharge using gas detectors (GASTEC, GV-100).
Figure 1. Schematic of atmospheric pressure discharge device. We employed bread yeast (Saccharomyces cerevisie) for the plasma irradiation experiments because of three reasons: (i) It i
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