S4-6

Applications of Multi- Phase-Media Plasma for Agriculture andFisheries
マルチフェーズプラズマの農水分野応用Koichi Takaki
高木浩一
Iwate University, 4-3-5 Ueda, Morioka, Iwate 020-8551, Japan
岩手大学 〒020-8551 岩手県盛岡市上田4-3-5

Multi-phase-media plasmas were produced using pulsed power technologies and were utilized in agriculturaland fisheries applications. Magnetic pulse compression (MPC) type pulsed power generator was employed
to produce a corona discharge plasmas in air-water mixture layers. Growth rate of Brassica rapa var.
perviridis (Chinese cabbage) was improved by use of the water after the plasma treatment in the bed-soilcultivation. Nitric acid ions were produced in the water after the plasma treatment. Nitrogen content in theleaves increased by the plasma treatment based on chlorophyll content analysis. The non-thermal plasmas
were also generated in gas-solid mixture using a Cockcroft-Walton circuit with small capacitance capacitor.
The plasma ignition changes an electric field distribution in vicinity of the plasma. The electrostatic force
around the solid material works as keeping freshness of agricultural and marine products owing to thecollection of fungi spores and the structure change of albumin in the cell membrane. Fruit body formation ofmushroom is also accelerated by the plasma ignition on the cultivation sawdust-bed. The high electric fieldis caused in the sawdust-bed and is worked as stimulation for the mushroom hypha. The response of thestimulation was confirmed by laccase analysis.

1. Introduction
Repetitively operated compact pulsed power
generators with a moderate peak power weredeveloped for the applications in several stages ofagriculture and fishery. Types of pulsed power thathave biological effects are caused with gas
discharges, water discharges, and electromagnetic
fields. The discharges yield free radicals, UV
radiation, intense electric field, and shock waves.
Biologically based applications of pulsed power are
performed by selecting the type that gives the target
objects the adequate result from among these agents.
For instance, intense electric fields form pores on thecell membrane, which is called electroporation [1],or influence the nuclei. The radicals in water reactwith cell membrane of bacteria. These applicationsare mainly based on biological effects and can becategorized as germination of plant seeds; control ofgrowth rate of the plants [2]; improvement ofmushroom yield [3]; keeping freshness for a
relatively longer period of perishables such as fishand shellfish [4]; decontamination of air and liquid
to inhibit degradation of agricultural products [5].
These applications can contribute a food supply
chain in Japan and the world.
2. Aqua-plasma for plant growth improvement
Figure 1 shows still photographs of the discharge
generated in the gas and liquid phases. The distancefrom high-voltage wire to liquid layer is 9 mm. The

streamer discharge initiates at vicinity of the center
wire and propagates toward the water layer byapplying 9kV pulse voltage generated with the MPC
generator [6]. It is clear that the streamer propagates
into the bubble through the tiny holes of the separator
from the wire electrode.
Figure 2 shows photographs of Brassica rapa var.
perviridis at 28 days of cultivation for various
plasma treatment times [6]. The plasma wasirradiated in the drainage water for 10 and 20
minutes each day. One group consisted of threecultivated pots. Another group (the control) wascultivated without plasma treatment. All plants grewby 28 days cultivation. The leaf size of the plants
increased with plasma treatment time. The use ofplasma in the water can supply many kinds ofchemical species, such as OH, O, O3, NO2, NO3, andH2O2, among others. Nitrate and nitrous species inFig. 1. Typical photograph of streamer discharges:
upper is in liquid and lower in gas phases.

the drainage water were measured to clarify theeffect of plasma irradiation on the plant growth rate
because nitrous nitrogen typically works as afertilizer in plant cultivation [2].

10 m

10 m

Fig. 3. Photographs of Brassica rapa var. perviridis
cultivated for 28 days at (a) w/o plasma and with (b)10 min. or (c) 20 min. treatment per day.

3. Gas-solid plasma for fruit body formation
Figure 3 shows a still photograph image of thedischarge from high-voltage electrode to sawdustbed for L. edodes cultivation. The distance fromelectrode to the sawdust-bed (solid layer) is 10 cm.
The discharge plasma bridges between the highvoltage electrode and the sawdust-bed. As the result,the surface potential of the sawdust-bed changes
from zero to the high-voltage. This potential change
causes high electric field in the sawdust-bed. The
hypha of the L. edodes are accelerated owing to thestrong electrical field [3].
Figure 4 shows scanning electron microscope(SEM) images of hyphae before and after applying
pulse voltage. It is confirmed that some parts of thehyphae are ruptured with force generated with thepulse electric field. The application of the pulseelectric field generates the forces to the hyphae.
Many parts of the hyphae are displaced by the force
and some hyphae are ruptured. This is candidate oftriggering fruit body formation.

Fig. 4. SEM images of Lentinula edodes hypha
before (top) and after (bottom) applying 10 kV
pulse high-voltages.

4. Preservation of marine products
AC electric field was used to improve a freshnessof perishable food such as purple sea urchin. Figure
5 shows the gel electrophoresis profile obtained by
the SDS-PAGE analysis. For the group which did not
apply the AC electric field at the time of a freeze, theamount of molecules with the molecular weight ofless than 70000 has increased, and the amount ofmolecules with the molecular weight of
150000~180000 has decreased. This indicates theprotein decomposition which means digestion [6].

Fig. 5. Gel electrophoresis profiles. [Output voltage
in freezing / in defrosting].

Fig. 3. Photographic image of discharge from highvoltage electrode to the sawdust-bed for L. edodes
cultivation.

References[1] A. Nakagawa et al.: IEEJ Trans. FM, 133 (2013) 32.
[in Japanese][2] K. Takaki et al.: J. Phys. Conf. Series, 418 (2013)
012140.
[3] K. Takaki et al.: Microorganisms, 2 (2014) 58.
[4] T. Ito et al.: J. Adv. Oxid. Technol. 17 (2004) 249.
[5] S. Koide et al.: J. Electrostatics, 71 (2013) 734.
[6] K. Takahashi et al.: IEEE Trans. Plasma Sci. 38(2010) 2694.