Effect of light-emitting diodes on the production of cordycepin, mannitol and adenosine in solid-state fermented rice by Cordyceps militaris

The effects of different light-emitting diode (LED) conditions including different LED wavelengths and LED wavelength combinations on the production of bioactive compounds of Cordyceps militaris cultivated on brown rice were investigated. The results of our study showed that the optimal illumination times for biomass (0.49 g/g dw, dry weight), cordycepin (3′-deoxyadenosine) (3.97 m g/g dw), mannitol (21.3 mg/g dw) and adenosine (0.95 m g/g dw) production were 12, 12, 12 and 8 h/day, respectively, by fluorescent lamps. Among the three different LED wavelengths tested, the greatest effect of wavelength for biomass (0.38 g/g dw), cordycepin (2.89 m g/g dw), mannitol (23.6 mg/g dw) and adenosine (0.76 m g/g dw) production were red light (619-626 nm), green light (526-531 nm), red light and blue light (467-472 nm), respectively. Among the ten LED wavelength combinations, the greatest effect of wavelength ratios for specific productivity of cordycepin (30.0), mannitol (86.5) and adenosine (5.5) were 3R:3B,2R:4B and 2R:4B, respectively. Our findings suggest that the combination of wavelengths had the greatest impact on the bioactive compounds production of C. militaris.