Carotenoid Production by Caterpillar Medicinal Mushrooms, Cordyceps militaris (Ascomycetes) under Different Culture Conditions

Cordyceps militaris, a well-known edible and medicinal species, is a potential source of natural carotenoids. The optimized conditions for carotenoid production are important for high-quality cultivation since carotenoid contents are the key factors for the appearance of fruiting bodies. In this study, carotenoid production by C. militaris under different culture conditions was compared. It was found that two-stage culture and fruiting body cultivation were suitable for the carotenoid production. Light is one of the important factors for carotenoid accumulation in this fungus and carotenoid can be produced by continuous shaking under light irradiation. Blue light with intensity of 17.3-64.3 lux can promote carotenoid production under the three tested culture methods. The carotenoid content was 4410.42 ± 30.83 and 3747.92 ± 178.13 μg g-1 under blue light intensity of 64.3 lux for the velum under two-stage culture and fruiting body cultivation, respectively. Oat medium may be suitable for the cultivation of fruiting bodies due to its high carotenoid production compared with other grains such as rice, wheat, and millet. Oxygen vector and oxidative stress induced by hydrogen peroxide can promote carotenoid production significantly under the two-stage culture. The carotenoid extracted from C. militaris showed strong antioxidant activity with IC50 value of 0.219 ± 0.01 mg ml-1, even higher than that of BHT, a positive control. This study will benefit the high-quality cultivation of this fungus and confirm that the carotenoid from C. militaris has the potential to be developed as a health food.