Zeaxanthin Production by an Antarctic <i>Flavobacterium</i> sp.: Effect of Dissolved Oxygen Concentration and Modeling Kinetics in Batch and Fed-Batch Fermentation

Zeaxanthin is a high-value carotenoid, found naturally in fruits and vegetables, flowers, and microorganisms. <i>Flavobacterium</i> genus is widely known for the production of zeaxanthin in its free form. Nowadays, the production of zeaxanthin from bacteria is still noncompetitive with traditional methods. The study of different operational conditions to enhance carotenoid production, along with the development of better models, is critical to improve the optimization, prediction, and control of the bioprocess. In this work, the influence of dissolved oxygen concentration was studied on zeaxanthin, β-cryptoxanthin, and β-carotene production. It was found that 10% pO₂ was the best condition for zeaxanthin production in a batch bioprocess, reaching a total carotenoid concentration of 3280 ± 88 μg/L, with 86% of zeaxanthin. To enhance carotenoid production, a fed-batch culture was performed. Although biomass and total carotenoid productivity were similar between batch and fed-batch processes, the total carotenoid concentration in the fed-batch was the highest (8.3 mg/L) but with lower zeaxanthin content and productivity. Two kinetic models were proposed based on a modified Monod and Luedeking-Piret model, as well as glucose, biomass, oxygen, and each carotenoid concentration mass balance. The binary model that considers oxygen in biomass growth and product formation presented a better fit to the experimental data.