23P018-O
Growth promotion characteristics of bread yeast
by atmospheric pressure dielectric barrier discharge plasma irradiation
大気圧バリア放電プラズマ照射による酵母の成長促進特性	 
Satoshi Kitazaki, Kazunori Koga, Masaharu Shiratani, and Nobuya Hayashi
北﨑	  訓1, 古閑一憲1，白谷正治1，林	  信哉21. Graduate School of Information Science and Electrical Engineering, Kyushu University
744, Motooka, Nishi-ku, Fukuoka 819-0395, Japan
九州大学	  大学院システム情報科学府 〒819-0395	  福岡市西区元岡744
2. Faculty of Science and Engineering, Saga University
1, Honjo-machi, Saga 840-8502, Japan
佐賀大学	  理工学部	  〒840−8502	  佐賀市本庄町1
We have investigated growth promotion of bread yeast (Saccharomyces cerevisie) by atmospheric pressure
dielectric barrier discharge plasma irradiation. NO of 70 ppm and O3 above 200 ppm are produce by theDBD plasmas. DBD discharge plasma irradiation of 50 and 100 s enhances the growth of yeast in the lagphase. At t = 1000 min in the lag phase, the absorbance of yeast with 50 s plasma irradiation is 3 times
higher than that without plasma irradidation. There is an optimum duration of plasma irradiation for thegrowth promotion.

1. IntroductionNonthermal atmospheric pressure plasmas havebeen employed for biomedical processing
applications, because they provide high density
radicals at a low gas temperature [1-7]. Recently,
nonthermal atmospheric pressure plasmas as well
as low pressure plasmas have been employed for
growth promotion of plant cells [8-12]. Suchenhancement of cell proliferation by plasma
irradiation is useful in many fields of cancer
therapy, regenerative medicine, fermentationindustry, and so on. In this study, we havedeveloped a scalable atmospheric pressure
dielectric barrier discharge (DBD) device forbiomedical processing in a large area and have
employed the device to growth promotion ofbread yeast for fermentation applications.
2. 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 aceramic tube of 2 mm in outer diameter. The
electrodes were arranged parallel with each other ata distance of 0.2 mm. The discharge voltage andfrequency were 10 kV and 10 kHz, respectively.
Optical emission spectra from the discharge
plasmas were obtained with a spectrometer toobtain information on the radicals generated in theplasmas.
We employed dry yeast (Saccharomycescerevisie) for the plasma irradiation experiments.
The yeast of 0.01 g was placed 1 mm below theelectrodes. The discharge voltage and frequency
were 10 kV and 10 kHz, respectively. The plasma
irradiation was carried out in the air. The irradiation
duration Ton was 50, 100 and 150 s. After theirradiation, yeast was suspended in 1 ml yeast
extract peptone dextrose (YPD) medium andagitated with a vortex mixer. 1 µl of sample wasmixed with 199 µl YPD medium in a micro wellplate and cultivated using a shaking incubator at 30oC. To obtain growth curve of yeast time evolutionof 660 nm light absorbance of the samples wasmeasured with a micro plate reader.

Fig. 1. Schematic of atmospheric pressure dielectricbarrier discharge device.

0.35

20.3

absorbanceabsorbance

1.5
10.50control
50s
100s
150s

0500 1000 1500 2000 2500 3000

time (min)Fig. 2. Growth curve of dry yeast.

3. Results and Discussion
Optical emission measurements show emission
NO-γ at 200 - 250 nm ． Gas detector tube
experiments show NO of 70 ppm and O3 above 200ppm at 10 mm below the electrodes produced by
the DBD discharge plasmas.
Figure 2 shows the growth curve of dry yeast.
For the control, the absorbance is almost constantuntil t = 1000 min. after the beginning of thecultivation, which corresponds to the lag phase, andthen it exponentially increases with t, theexponential growth phase. For yeast with theplasma irradiation of 50 and 100 s, the absorbanceincreases from t = 0 min. At t = 1000 min., themaximum absorbance for Ton = 50 s is 3 times ashigh as that for the control (see Fig. 3). After t =1000 min., the absorbance increases exponentiallywith t. For longer Ton of 100s and 150s, the yeast isinactivated and hence it growth is suppressedcompared to the control. These results suggestthat the DBD plasma irradiation reduces the lagphase of yeast cell division and there is an optimum
duration of plasma irradiation for the growthpromotion.
4. Conclusions
We have investigated growth promotion
characteristics of bread yeast by atmosphericpressure dielectric barrier discharge plasma
irradiation. We obtained the following conclusions:
1) NO of 70 ppm and O3 above 200 ppm areproduce by the DBD plasmas.
2) DBD plasma irradiation of 50 and 100 senhances the growth of yeast in the lag phase.
3) At t = 1000 min in the lag phase, theabsorbance of yeast with 50 s plasma
irradiation is 3 times higher than that without
plasma irradiation.

0.25
0.2
0.15
0.1
0.05
00250

500

time (min)

750

1000

Fig. 3. Growth curve of dry yeast in lag phase.

4) There is an optimum duration of plasma
irradiation for the growth promotion.
Acknowledgment
This work was partly supported by the Japan
Society for the Promotion of Science (JSPS).
References[1] B. Sera, P.Spatenka, M. Sery, N. Vrchotova, andI. Hruskova: IEEE Trans. Plasma Sci. 38(2010) 2963-2968.
[2] B. Sera, V. Stranak, M. Sery, M. Tichy, and P.
Spatenka: Plasma Sci. Technol. 10 (4) (2008)506.
[3] D. Dobrynin, G. Fridman, G. Friedman, and A.
Fridman: New J. Phys. 11 (2009) 115020.
[4] J. H. Loh: Med Device Tecnol. (1999)[5] S. Kitazaki and N. Hayashi: IEEE Trans. Plasma
Sci. 36 (2008) 1304.
[6] M. K. H. Ebrahim: Acta agronomica Hungarica
52 (2004) 113.
[7] J. C. Volin, F. S. Denes, R.A. Young, and S.M.T.
Park: Crop Sci. 40 (2000) 1706.
[8] K. Takaki and S. Ihara: IEEJ Trans. FM 129(2009) 439 [in Japanese].
[9] S. U. Kalghatgi, A. Fridman, G. Friedman, andA. M. Clyne: Proc. IEEE Eng. Med. Biol. Soc.
(2009).
[10] N. Hayashi, A. Nakahigashi, M. Goto, S.
Kitazaki, K. Koga, and M. Shiratani: Jpn. J.
Appl. Phys. (in press).
[11] S. Kitazaki, D. Yamashita, H. Matsuzaki, G.
Uchida, K. Koga, and M. Shiratani: Proc. IEEETENCON 2010 (2010) pp.1960-1963.
[12] S. Kitazaki, K. Koga, M. Shiratani, and N.
Hayashi: Jpn. J. Appl. Phys. (in press).