Optimization of Algal Culture Medium for Zeaxanthin Production by Dunaliella tertiolecta : An RSM based Approach

The Chlorophycean microalgae Dunaliella have gained commercial interest because of the synthesis of highly valuable products. One among them is zeaxanthin, a xanthophyll carotenoid valued for its nutraceutical potential related to prevention of age-related macular degeneration and cataract, which is the primary cause for blindness. To improve zeaxanthin production by the microalgae Dunaliella tertiolecta (NIOT-141), De Walne’s medium was optimized to its most favourable nutrient level using response surface methodology (RSM) approach. Plackett–Burman method was employed to screen the most significant nutrients influencing zeaxanthin accumulation which revealed sodium nitrate, trace metals and sodium dihydrogen phosphate as the crucial medium components for increasing zeaxanthin production (P < 0.05). Further, RSM was employed to study the interaction between these factors and identify optimum concentration of the significant ingredients for higher zeaxanthin production. The highest zeaxanthin production reached 20.2 ± 1.29 mg l^–1 under the optimal conditions of 910 mg l^–1 NaNO₃, 40.5 mg l^–1 NaHM₂PO₄ and 0.605 mg l^–1 trace metals solution. Moreover, validation of optimized medium resulted in a three-fold increase in zeaxanthin production compared to unoptimized Walne’s medium (6.72 ± 0.22 mg l^–1). The results thus obtained were more analogous to the predicted values. Hence the model is effective for enhancing zeaxanthin production in D. tertiolecta.