Optimization of carotenoids production by red yeast sporobolomyces pararoseus TISTR5213 using waste glycerol as the sole carbon source

Abstract

The usage of waste glycerol obtained from biodiesel production is a big challenge as this glycerol is not suitable for foods and cosmetics applications. Therefore, nine strains of red yeasts from the culture collection of Thailand Institute Scientific and Technological Research (TISTR) were screened for carotenoids production in yeast malt-extract medium (YM), basal medium supplemented with either pure glycerol (BMP) or waste glycerol (BMW) as the sole carbon source. The results showed that Sporobolomyces pararoseus TISTR5213 produced the maximum of total carotenoids at 4.87±0.08, 1.58±0.44 and 1.77±0.02 mg/L, in YM, BMP and BMW, respectively. Variable medium components of BMW were selected in accordance with the Plackett-Burman experimental design with only one factor of waste glycerol being significant. The optimization conditions for physical factors (pH and temperature levels) were then combined in further studies through the response surface methodology (RSM) approach. A quadratic model was constructed by central composite design (CCD). Using this experimental design, the total carotenoids production yield increased from 1.77 to 16.55 mg/L or about 835% higher than un-optimized BMW. The optimum conditions to achieve maximum yield of total carotenoids were; waste glycerol 34.00 g/L, initial pH at 5.64 and 23.90°C for 5 days. In comparison, the cost of carotenoids production in YM, BMP and optimized BMW were; 12.08±2.68, 15.69±4.41 and 0.90±0.02 Baht/mg carotenoids/L medium, respectively.