Bulletin Number 15. July 31st, 2016

The mushroom industry in Japan – technological and scientific shifts from the past to the present

Yutaka Kitamoto, Member of Agricultural Academy of Japan and Former Member of Science Council of Japan (Chair of Microbiology)

   The mushroom industry in Japan developed dramatically from the middle of the 1960s, after the beginning and spread of bottle cultivation for wood rotting mushrooms. Four major technological developments contributed to the remarkable expansion of the mushroom industry in the following several decades: the establishment of bottle cultivation technology for Flammulina velutipes (Enokitake) and Hypsizygus marmoreus, the innovation of the white Enokitake strainby breeding, the development of bag cultivation technology for Lentinula edodes and Grifola frondosa, and the innovation and improvement of automated machinery essential for large-scale bottle and bag cultivation by Japanese manufacturers. Annual production of cultivated mushrooms in Japan attained about 482 thousand tons (fresh weight) in 2011, and has been maintained at almost the same scale thereafter. The major mushroom species in the early period of development were Lentinula edodes, Flammulina velutipes, Pleurotus ostreatus and Pholiota microspora. However, the production trends are now in the order of Flammulina velutipes, followed by Lentinula edodes, Hypsizygus marmoreus, Grifola frondosa and Pleurotus eryngii. Weakness in private demand and an increase in cost of electricity after the nuclear accident at Fukushima in March of 2011 strongly increased the demand for the promotion of technology for further cost reduction.
   More than 90 percent of cultivated mushrooms are the products of mushroom factories in Japan. Environmental measuring and control systems for cultivation facilities have been essentially equipped to produce high quality mushrooms by year-round cultivation. The environmental requirements for successive cultivation stages, as found from physiological research on mushrooms, should provide an ideal situation for mushroom cultivation. However, most knowledge is not the result of scientific studies, but has been provided by the trial-and-error of innovative farmers at Enokitake and Hiratake (oyster mushroom) cultivation sites in the early progressive period, before the 1980s. Application of trial-and-error to searching for the most suitable environmental controls at successive stages of mushroom cultivation can now be performed by some large-scale mushroom producers in Japan due to their ability to invest in current facilities and the latest machinery. However, it is difficult for small and medium producers in the constrained business situation. Given the present situation, the promotion of environmental control technology based on the physiology of mushrooms must be a firm strategic move for attaining sustainable mushroom production in Japan.
   The essential environmental factors for the running of mushroom factories are temperature, humidity, indoor wind velocity, atmospheric gas contents and light irradiation. The mushroom business needs to optimize environmental control systems for high productivity and high quality in mushroom production to improve profitability. However, our current knowledge of the individual environmental factors described above is still too small, and the quality of knowledge is low from a scientific point of view. For example, there is no scientific verification of the superiority of constant temperature control versus temperature control in mushroom production due to daily changes in atmospheric conditions. We have little knowledge on the effect of carbon dioxide on the shape and food quality of fruit bodies of mushrooms at the physiological, biochemical or molecular levels, although the effects of the gas are definitive on both productivity and the market price of commercial mushrooms. On the other hand, there has been research on the effect of light on the fruiting of mushrooms by some Japanese scientists over several decades. The application of LED irradiation to fruit body production in Flammulina velutipes appeared in an early technological archive of a Japanese researcher, and this knowledge was widely applied to the production of various species of mushrooms during the past decade after the decline in price of LED equipment for mushroom industrial use. In response to this concern, a group of mushroom scientists in Japan began research on the signal mechanism in the photomorphogenetic event in fruit body formation. In addition, little is known about the influence of the circadian rhythm on the effect of fruit body formation in mushrooms except for some basic research using Coprinus and Polyporus species as test materials. However, no applicable literature on this topic has been found for commercial mushroom cultivation. Basic research on individual environmental factors at cultivation sites must contribute to the further improvement of productivity in mushroom factory production as well as to raising the quality of commercial mushrooms.
   The major subject remaining to be solved for the mushroom industry in Japan is the development of hardware for intelligent environmental control of mushroom facilities to improve the business. The choice of a constant temperature setting for spawn running in mushroom cultivation stages is reasonable for mushroom cultivation in factories. However, judging from the production cost, we do not have any evidence that a constant temperature setting is more favorable than a temperature control mimicking natural daily changes. If we introduce the temperature control similar to the daily natural changes for the developmental stages of fruit bodies in mushroom facilities, the reduction in the difference between indoor and outdoor temperatures should contribute to a reduction in electric power load for air conditioning of the mushroom facilities. A rough calculation suggests more than a 15% cost reduction in running the mushroom factory. For further energy savings in mushroom production, the Lossnay energy recovery ventilator (a product of Mitsubishi Electric Co.) is standard equipment that could reduce electric power consumption from air conditioning by more than 40%. The introduction of intelligent temperature control machinery combined with a variable temperature air conditioning system could decrease the total production cost by more than 10% regardless of further investment.
   Sophistication in the control of the gas environment of cultivation facilities is a key point in mushroom factory production, as is intelligent temperature control to influence the productivity and the quality of the mushrooms directly. If the carbon dioxide concentration is high, the stipe abnormally elongates, the pileus becomes smaller, and the quality decreases. Mushroom facilities usually set an amount of ventilation by trial-and-error, which can be a little too high during cultivation after the initiation of fruit bodies. Scientific surveys of the influence of carbon dioxide concentration on productivity and quality in mushroom production at experimental sites followed by scaled-up testing at the mushroom facility may allow further cost reduction in factory production. Research and development on intelligent, complex environment control systems involving the items listed above may be undertaken in due course by mushroom technologists. Further development of the mushroom industry relies on the understanding the effect of gases on fruit bodies of mushrooms, as well as close collaboration between mushroom scientists and engineers to establish total intelligent environment control systems.

The first white registered strain (M-50) of Flammulina velutipes innovatedby the author

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