Chemical Engineering
Zeaxanthin is a pigment of great commercial importance due to the diversity of applications in the food industry, including poultry, pharmaceutical, dairy, and bakery. To achieve optimisation of the microbiological production of zeaxanthin, strain passport ATCC 21588 of Flavobacterium sp. was used in the present study, which was carried out by means of the fermentation technique of cell suspension culture submerged in an culture medium to inoculum ratio at a concentration of 5-10%, in a 14-L stirred tank reactor. A central composite design by Box-Behnken (15 treatments) was used to investigate the effects of aeration, mixing and the inoculum to culture medium ratio. The nutrients in the culture medium were: carbon source (corn steep liquor), nitrogen (NH4Cl), phosphorus (KH2PO4), maintaining a constant magnesium concentration of 1.5 g/L and trace elements of 0.5 ml/L; the operating conditions were: temperature (27 °C), pH (7), agitation speed (200-400 rpm), aeration (0.6-0.9 vvm). The analysis of variance and the response surface graphs of the data obtained show that the most significant factors are: aeration and mixing, with a confidence level of 95%. The statistical analysis produced the optimal conditions for the production of zeaxanthin in a relatively short time; the values were: aeration speed 0.680 vvm, agitation speed 264 rpm, and with this information it was possible to obtain an optimum value of 56.865 ppm of zeaxanthin, with a productivity of 1420 mg/(L/h) in a fermentation time of 40 h and with an inoculum to culture medium ratio of 7.56.