Zeaxanthin Production\nby an Antarctic <i>Flavobacterium</i> sp.: Effect of Dissolved\nOxygen Concentration and Modeling Kinetics\nin Batch and Fed-Batch Fermentation

Zeaxanthin is a high-value carotenoid, found naturally\nin fruits\nand vegetables, flowers, and microorganisms. <i>Flavobacterium</i> genus is widely known for the production of zeaxanthin in its free\nform. Nowadays, the production of zeaxanthin from bacteria is still\nnoncompetitive with traditional methods. The study of different operational\nconditions to enhance carotenoid production, along with the development\nof better models, is critical to improve the optimization, prediction,\nand control of the bioprocess. In this work, the influence of dissolved\noxygen concentration was studied on zeaxanthin, β-cryptoxanthin,\nand β-carotene production. It was found that 10% pO<sub>2</sub> was the best condition for zeaxanthin production in a batch bioprocess,\nreaching a total carotenoid concentration of 3280 ± 88 μg/L,\nwith 86% of zeaxanthin. To enhance carotenoid production, a fed-batch\nculture was performed. Although biomass and total carotenoid productivity\nwere similar between batch and fed-batch processes, the total carotenoid\nconcentration in the fed-batch was the highest (8.3 mg/L) but with\nlower zeaxanthin content and productivity. Two kinetic models were\nproposed based on a modified Monod and Luedeking–Piret model,\nas well as glucose, biomass, oxygen, and each carotenoid concentration\nmass balance. The binary model that considers oxygen in biomass growth\nand product formation presented a better fit to the experimental data.