Abstract:
Carotenoids are natural pigments found in many fruits and vegetables. These important nutrients play significant roles in mental and physical health of humans. The advantages of microbial production of carotenoids are short cycles, easy to retrieve, and not affected by climate. For this study, a colony of pigment-producing red yeast, Rhodotorula mucilaginosa, was screened from fruits and vegetables as a strain of fungi with the potential to produce carotenoids. This study discussed the optimization of carotenoid production in Rhodotorula mucilaginosa. A 0.1% inoculum of the yeast was shaken in a shake flask at 125 rpm. The controlled conditions of culture were the following: temperature, 27.5˚C; pH 5.0; carbon source, 15 g/L glucose; and nitrogen source, 2.5 g/L yeast extract. The optimal time for pigment collection was 24 hours after the yeast had reached the stationary phase of growth. Pigment production was 1469.29 μg•L−1. When a culture is subjected to stress, its biomass and physiological metabolism changes. Therefore, after the culture had reached the stationary phase of growth, different amounts of stress were applied to obtain higher pigment accumulation. The stress conditions tested included a six-hour short-term high temperature of 37˚C, a six-hour short-term low temperature of 10˚C, and cultivation at a sustained low temperature of 22.5˚C. The results showed that short-term temperature changes could not effectively increase pigment accumulation in yeast cells. After 72 hours of incubation, continued cultivation at a sustained low temperature of 22.5˚C could increase pigment production to a maximum of 1533.27 μg•L−1. High pigment production was prolonged and sustained, while degradation of pigment slowed. The results of this study can potentially be used in future in continuous fermentation to extend high pigment yield times and sustain pigment production.