Optimization of astaxanthin production by Phaffia rhodozyma through factorial design and response surface methodology

Sequential methodology based on the application of three types of experimen tal designs was used to optimize the astaxanthin production of the mutant s train 25-2 of Phaffia rhodozyma in shake flask cultures. The first design e mployed was a factorial design 2(5), where the factors studied were: pH, te mperature, percent of inoculum, carbon and nitrogen concentrations, each on e at two levels. This design was performed in two medium types: rich YM med ium and minimal medium, based on date juice (Yucca medium). With this first design the most important factors were determined (carbon concentration an d temperature) that were used in the second experimental strategy: the meth od of steepest ascent was applied in order to rapidly approach the optimum. Finally, a second-order response surface design was applied using temperat ure and carbon concentration as factors. The optimal conditions stimulating the highest astaxanthin production were: 19.7 degreesC temperature; 11.25 g l(-1) carbon concentration; 6.0 pH; 5% inoculum and 0.5 g l(-1) nitrogen concentration. Under these conditions the astaxanthin production was 8100 m ug l(-1), 92% higher than the production under the initial conditions. (C) 2001 Elsevier Science B.V. All rights reserved.