| Summary: | 博士 === 大葉大學 === 食品暨應用生物科技學系 === 107 === Cordyceps militaris, also known as “pupa grass” and “caterpillar fungus.” is considered an artificially cultivated substitute for Ophiocordyceps sinensis in China. In traditional Chinese medicine and healthcare, Cordyceps militaris has advantages such as mild medicinal effects and notable physiological activity. Light-emitting diodes (LEDs) consume one-eighth of the electricity of incandescent light bulbs and half the energy of fluorescent lamps. In recent years, under the global trend of energy conservation, the use of LED lamps has rapidly risen in the light source domain; LEDs have beneficial characteristics, such as the emission of light with a narrow wavelength and cold light, for the cultivation of Cordyceps militaris.
In this study, Cordyceps militaris was used as the subject to examine the effects of LED wavelength and intensity, variations in light cycle conditions, and liquid-state and solid-state quantitative fermentation on the yield of active ingredients in order to identify suitable culture conditions for synthesizing many active ingredients and effects on the fruiting body morphology. To overcome the gap between the internal and external temperature and humidity conditions in bottles, we developed a “proximal sensing device” that is combined with Internet of Things technology to directly evaluate culture conditions inside the bottles and assist the precise control of environmental conditions. With regards to fruiting body morphology, red and green LEDs can shorten the primordium formation period and fruiting body maturation period. Red LED increased the number of primordia in all bottles as well as the biological efficiency. The red and blue LEDs increased the fruiting body weight in all bottles. In addition, as light intensity increased, the mean number of primordia in every bottle gradually increased and the fruiting body maturation period was also shortened. In addition, as the light intensity increased, the biomass and biological efficiency of the fruiting bodies also increased. This shows that the biomass and biological efficiency of the fruiting bodies are associated with light intensity.
With regards to the physiologically active ingredients, the study results showed that the maximum levels of cordycepin, adenosine, mannitol, and polysaccharides were 15.63 ± 0.72 mg/g (100 lux), 23.17 ± 1.22 mg/g (1000 lux), 19.84 ± 0.84 mg/g (300 lux), and 28.69 ± 1.52 mg/g (1000 lux), respectively, when a combination of red and blue LEDs in a ratio of 8:1 and a light cycle of 16 h/8 h (day/night) were used during culture and when solid-state fermentation of Cordyceps militaris was carried out.
For liquid-state fermentation, different types of bean (soy beans, green beans, red beans, black beans, and peas) matrices were used as culture medium. We compared the applicability of different types of bean sprout juices, germination solutions, and soybean milk culture medium. We found that the yield of the major product, γ-aminobutyric acid, and other amino acid neurotransmitter by-products (glutamic acid, aspartic acid, and glycine) could be greatly increased by adjusting the ratio of nitrogen and carbon sources in the fermentation medium, optimizing culture conditions (initial culture pH, oscillation rate), and controlling the pH in the culture medium in the fermentation tanks. We found that when a red bean-based germination medium was used for shake-flask fermentation of Cordyceps militaris, the GABA yield was 240.28 mg/100 g and glycine yield was 12.81 mg/100 g. When a 750-L fermentation tank and soybean matrix was used with a rotation speed of 45 rpm, we found that an optimal GABA yield of 961 mg/100 g was obtained, while the yields of cordycepin, adenosine, and polysaccharides were 42.93 mg/100 g, 5.75 mg/100 g, and 2.07 g/100 g, respectively.
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