Developing a Novel Two-Stage Process for Carotenoid Production by Cordyceps militaris (Ascomycetes)

Natural carotenoids are attracting increasing interest, but their widespread use is limited because of poor production. Cordyceps militaris, a traditional Chinese mushroom, contains a large amount of carotenoids, and this study aimed to increase carotenoid production by C. militaris by optimizing a liquid-state cultivation system. We developed and optimized a novel 2-stage process, including cultivation under shaking in darkness and under static irradiation on a flat panel, using response surface methodology, and we compared this process to common shake-flask cultivation. In addition, we examined the effects of different inducers (chitosan, peanut oil, tomato juice, yeast, and metal ions) on carotenoid production. Results showed that under optimal conditions (4 days of shaking in darkness, 10 days of static irradiation with a 100-mL flat panel volume), a maximum of 1217.5 ± 115.9 μg/g carotenoids were produced; only 662.9 μg/g were produced by common shake-flask cultivation. Only a large amount of chitosan (8 mg) could significantly increase carotenoid content; some of the other inducers showed inhibitory effects. This study demonstrated that this 2-stage process could effectively increase the natural carotenoid content in C. militaris, making it a potential source for commercial exploitation.