Simplex optimization of carotenoid production by Rhodotorula glutinis using hydrolyzed mung bean waste flour as substrate

The sequential simplex method was employed for the optimization of growth and carotenoid production in the yeast Rhodotorula glutinis using a substrate containing hydrolyzed mung bean waste flour from glass noodle production as the principal nitrogen source and sweet potato extract as the principal carbon source. Six experimental parameters were used: concentration of mung bean waste flour, concentration of sweet potato extract, pH, temperature, agitation rate and cultivation time. Under optimized conditions the cell dry weight was 10.35 ± 0.13 g/l and the total carotenoid content was 3.48 ± 0.02 mg/l using 23.63 g/l of H2SO4-hydroyzed mung bean waste flour, 51.76 g/l of sweet potato extract, pH 5.91, 30.3 °C, agitation rate of 258 rpm and incubation time of 94.78 h. These results for cell dry weight and carotenoid content were, respectively, 43 and 20% higher than could be obtained by varying one factor at a time. The present work demonstrates the effectiveness of using a widely available agro-industrial waste product as substrate and the efficiency of the sequential simplex optimization method in obtaining high yields.