Fruit-body yield of
Abstract
High-voltage electrical stimulation is effective for promotion of fruit-body development in mushroom cultivation. The high voltage applying to cultivation bed of mushroom generates intense electric field inside the bed substrate. The intense electric field accelerates the hypha move owing to the electrostatic force. As a result, some parts of hyphae are cut and scratched. The cutting and scratching of hypha work as stimulation for promotion of the fruit-body development. The promotion effect of high-voltage stimulation to sawdust-based substrate of L. and natural logs hosting Lentinula edodes, Pholiota microspora and Hypholoma lateritium are confirmed through the experiment in the cultivation field. The fruit-body formation of mushrooms increases 1.3–2.0 times in terms of the total weight. The accumulated yield of L. edodes for four cultivation seasons is improved from 160 to 320 g by applying high voltage of 50 or 100 kV. However, the yield decreases from 320 to 240 g upon increasing applied voltage from 100 to 130 kV. The yield of the other types of mushrooms shows tendencies similar to those of L. edodes by applying high voltage. An optimal voltage exists for efficient fruiting body induction.
Keywords
- fruit-body development
- mushroom cultivation
- high-voltage methods
- electrical stimulation
- L. edodes
- Pholiota microspora
- Hypholoma lateritium
1. Introduction
Mushrooms such as
Physical phenomena in cells caused by external pulsed electromagnetic energy have a variety of applications on biotechnologies [1]. The electrical stimulation can either destroy the cells and plants or promote its growth rate, depending on the degree of stimulation. In nature, mushrooms extraordinary grow-up around a hit point of a lightning have been reported by some mushroom farmers. Early studies of mushroom growth promotion by artificial lightning were carried out on edible mushroom cultivation using an impulse generator [2]. The output voltage of the impulse generator was more than 500 kV. After that, the high-voltage pulsed power supplies were designed to generate an output voltage from 50 to 130 kV for the electrical stimulation on mushroom cultivation bed. The promotion effects of high-voltage stimulation on sawdust-based substrate of
![](http://cdnintech.com/media/chapter/62393/1512345123/media/F1.png)
Figure 1.
Typical photograph of the cultured
2. Mushroom cultivation and stimulation for fruiting body development
Mushroom is fruiting body mainly in basidiomycetous fungi and some ascomycetous fungi. Therefore, mushrooms are developed for spore formation. Multiple environmental factors such as light, temperature, nutrient, gaseous components influence fruiting body induction and development. These environmental factors are used for sensing appropriate conditions for spore formation and dispersal.
Condition for fruiting body induction is one of critical factor for mushroom cultivation. To establish high yield cultivation method, it is very important to understand effects of environmental factors for fruiting body induction. Environmental factors for fruiting body induction are classified into physiological and physical factors. Gaseous condition and nutrient, or hormones are classified as physiological factor, and wounding or striking as physical factors. Light is one of the important factors for fruiting body induction, and blue light is the effective wavelength. For example, light promotes fruiting body induction in
Wounding or striking are used for commercial cultivation in several mushroom species. For example, scrapping mycelia on surface of the media (so called Kinkaki in Japanese) is used for fruiting body induction in several mushrooms. Striking log wood is used for stimulation of fruiting body induction especially in
3. History of electrical stimulation for mushroom fruiting body development
The application of a pulsed high voltage to improve the yield in edible mushroom cultivation has also been attempted by some research groups. The fruiting capacity of shiitake mushroom (
Many types of electrical power supplies have been employed to provide electrical stimulation. A large scale 1 MV high-voltage impulse generator was used to stimulate
The mechanism driving the increase in the fruiting body formation by applying high voltage is not clear, but researchers have suggested two possible explanations. One is that the mushroom hyphae are ruptured by applying a high voltage. Physical damage to the hypha stimulates fruiting body formation in mushrooms [5, 7]. The other explanation involves the activation of enzymes. Some enzymes are activated by applying a high voltage, and consequently, mushroom fruiting bodies develop abundantly [2]. Some effects of the high-voltage stimulation were recognized using microscopic observation and chemical analysis. A scanning electron microscope observation indicated that the synthesis of crump connections was accelerated with electrical stimulation [2, 5]. Some types of enzymes, including
4. Laboratory test using impulse generator
Early stage of the study on mushroom fruiting promotion and large scale impulse generators was used as artificial lightning for stimulation on the mushroom fruiting promotion. In this section, the laboratory test of artificial lightning stimulation for fruiting body induction using impulse voltage is described.
Figure 2 shows typical photograph of an impulse generator [12]. The impulse generator consists of 10–20 capacitors, gap switches and damping resistors [13]. The capacitors are connected in parallel at charging phase. After charging up the capacitors, the connection of the capacitors is changed from parallel to series using the gap switches. As a result, the output voltage is multiplied by changing the connection of the capacitors. Typical output voltage is in range from 250 kV to 1 MV. The rise time of the output voltage is controlled around the microsecond-order as an artificial lightning stroke voltage. The example of the applied voltage to the bet-log is shown in Figure 3 [2]. The peak voltage of 288 kV is generated by operating the impulse generator. The rise time of the voltage is close to 0.5 μs as shown in Figure 3. In experiments, the bed-logs are connected to high-voltage electrode as shown in Figure 2. The bed-logs (Konara oak;
![](http://cdnintech.com/media/chapter/62393/1512345123/media/F2.png)
Figure 2.
Photograph of impulse generator at stimulation on shiitake mushroom cultivation bed-log [
![](http://cdnintech.com/media/chapter/62393/1512345123/media/F3.png)
Figure 3.
288 kV output voltage of an impulse generator [
![](http://cdnintech.com/media/chapter/62393/1512345123/media/F4.png)
Figure 4.
Photographs of setup of bed-logs for impulse high-voltage stimulation [
Typical results of the stimulation on yielding rate of
Exp. group. | Number of exp. bed-logs | Fruit-body yield (per 1 m3 of wood) Number |
Dry wt (g) |
---|---|---|---|
144 kV | 2 4 | 505.3 | 1337.0 |
288 kV | 2 4 | 770.1 | 2171.4 |
576 kV | 2 4 | 121.6 | 558.4 |
Contd. | 2 4 | 16.9 | 55.2 |
Table 1.
Bed-log age: 38 months after inoculation (Yakult haru 2). Water content of bed-logs: 38.9% (mean value of six samples). All exp. groups had 34 mm rainfall in a week after discharge.
Exp. group. | Number of exp. bed-logs | Fruit-body yield (per 1 m3 of wood) Number |
Dry wt (g) |
---|---|---|---|
288 kV | 2 1 | 650.8 | 2100.0 |
576 kV | 2 1 | 485.8 | 1648.9 |
720 kV | 2 1 | 453.8 | 1427.4 |
Cont. | 2 1 | 276.2 | 840.6 |
Table 2.
Fruit-body yield of
Bed-log age: 38 months after inoculation (Yakult haru 2). Water content of bed-logs: 42.3% (mean value of six samples).
![](http://cdnintech.com/media/chapter/62393/1512345123/media/F5.png)
Figure 5.
Photographs of electrical discharge on surface of the bed-log and crack of the bed-logs by impulse high-voltage application [
The frequencies of the fruiting body yield by impulse high-voltage stimulation under same condition with Table 1 are shown in Figure 6 [2]. In the control case (without high-voltage stimulation), the fruiting body cannot be harvested for 20 bed-logs (83%). One fruiting body can be harvested from four bed-logs (17%). However, the fruiting bodies can be harvested from 21 bed-logs (except 3 bed-logs; 12%) at 288 kV impulse voltage applying. The decrease of number of the bed-log without
![](http://cdnintech.com/media/chapter/62393/1512345123/media/F6.png)
Figure 6.
Frequencies of the fruit-body yield by impulse high-voltage stimulation to
5. Field test using compact high-voltage generator
The impulse generator has huge size for utilization in mushroom-cultivating field as shown in Figure 2. Some types of compact high-voltage pulse generator were developed for promotion of the fruiting body formation on bed-logs or sawdust bed-blocks (substrate) of mushroom cultivation.
Figure 7(a) and (b) shows photograph and equivalent circuit of a compact pulsed power generator used for promotion of fruit-body formation in natural-log based mushroom cultivation [8]. An inductive energy storage (IES) system consists of a primary energy storage capacitor C, a closing switch GS, a secondary energy storage inductor L and an opening switch. A thin copper fuse is used as the opening switch to interrupt large current in short time. Figure 8(a) shows typical circuit current and output voltage waveforms at 12 kV charging voltage. The 8 cm-length fuse and the 15 μH-inductance secondary energy storage inductor are used. The current starts to flow after closing the switch GS with LC oscillation. The circuit current is interrupted after fuse melting phase within 50 ns. The output voltage increases rapidly and has a 120 kV maximum voltage. This output voltage corresponds to 10 times amplification. The high voltage pulse is produced by the total circuit inductance and rapid current interruption produces a high-voltage pulse expressed as
where
![](http://cdnintech.com/media/chapter/62393/1512345123/media/F7.png)
Figure 7.
IES pulsed power generator with fuse opening switch; (a) photograph and its circuit. (
![](http://cdnintech.com/media/chapter/62393/1512345123/media/F8.png)
Figure 8.
Typical waveforms of (a) circuit current though the fuse and output voltage at 12 kV charging voltage and (b) output voltage for various charging voltages [
Figure 9(a) shows the total weight of
![](http://cdnintech.com/media/chapter/62393/1512345123/media/F9.png)
Figure 9.
The cultured
Figure 10(a) and (b) shows photograph and equivalent circuit of a compact pulsed power generator based on combining IES with Marx circuit to reduce the primary charging voltage [14]. After charging up the four primary energy storage capacitors, the gap switches GS are triggered externally. The closing switch GS changes the connection of the capacitors from parallel to series. As a result, the voltage is multiplied from
![](http://cdnintech.com/media/chapter/62393/1512345123/media/F10.png)
Figure 10.
Marx-IES pulsed power generator with fuse opening switch; (a) photograph and (b) its circuit with fuse opening switch. (
![](http://cdnintech.com/media/chapter/62393/1512345123/media/F11.png)
Figure 11.
Typical waveforms of (a) circuit current though the fuse and output voltage at 5 kV charging voltage and (b) output voltage as a function of fuse length for various charging voltages of the primary energy storage capacitor [
Figure 12 shows the
![](http://cdnintech.com/media/chapter/62393/1512345123/media/F12.png)
Figure 12.
Total weight of cultured
Figure 13 shows the weights of
![](http://cdnintech.com/media/chapter/62393/1512345123/media/F13.png)
Figure 13.
Difference in the yield of fruit bodies of
Figure 14 shows the time history of the amount of mushrooms cultured under various stimulation conditions in the spring of 2009. The yield is normalized by the total crop weight for one harvesting season and is evaluated as an aggregate of all crops. The total crop weights were 60, 111, 90 and 89 g in the control, 50, 100 and 125 kV stimulation groups, respectively. Compared with the control group, the total yield increased when applying a voltage of 50 and 100 kV. The harvested weight for 15 days after the first crop (day 18) was approximately 50% of the total in the control group. However, the crop weight during this period increased to 86% of the total when applying voltages of 50 and 100 kV. This result indicates that the mushrooms can be harvested in fewer days by applying high voltage as electrical stimulation.
![](http://cdnintech.com/media/chapter/62393/1512345123/media/F14.png)
Figure 14.
Time-history of the total amount of harvested fruit bodies for various stimulation voltages [
Figure 15 shows the crop weight of
![](http://cdnintech.com/media/chapter/62393/1512345123/media/F15.png)
Figure 15.
Yield of
![](http://cdnintech.com/media/chapter/62393/1512345123/media/F16.png)
Figure 16.
Typical photographs of the cultured
6. Morphological changes after electrical stimulation
It is very difficult to reveal how electric stimulation affects fruiting body induction in mushroom species. Because molecular mechanisms for fruiting body induction in mushroom species have not still been well understood yet. Therefore, we focused on morphological changes after electrical stimulation.
Figure 17(a) and (b) shows images of
![](http://cdnintech.com/media/chapter/62393/1512345123/media/F17.png)
Figure 17.
Microscopic images of
Figure 18 shows typical photographs 10 days after cultivation at various amplitudes of the applied voltage. The pulsed voltage was applied after 5 days of cultivation of
![](http://cdnintech.com/media/chapter/62393/1512345123/media/F18.png)
Figure 18.
Influence of the pulsed voltage stimulation on hypha growth in agar medium cultivation. The diameter of the petri dishes is 10 cm in the all cases. The inner and outer dotted circles indicate growth positions of hyphae at 5- and 10-days cultivation, respectively [
7. Conclusions
High-voltage electrical stimulation on fruiting body formation in cultivating mushrooms was described. The compact high-voltage pulsed power supplies were developed for the electrical stimulation to promote fruiting body formation on cultivation bed-logs and sawdust substrate (bed-block). The promotion effects of high-voltage stimulation of sawdust-based substrate of
Securing profitability of the electrical stimulation is important for the widespread to the mushroom famers. The pulse voltage stimulation systems for improvement of mushroom yield have been developed and sold by some companies. Typical price of the stimulation system is around 5000 USD. The increment of
Acknowledgments
The authors of this chapter confirm that they have received permission to reuse all the tables and figures in their current work.
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