The Comparison of Lutein Production by Scenesdesmus sp. in the Autotrophic and the Mixotrophic Cultivation

The results of this study indicate that an increase in CO2 percentage to 30% can enhance Scenedesmus sp. growth in autotrophic cultivation to a maximum of 0.85 g/l as compared with 0.6 g/l obtained in the batch with air (after 6 days of cultivation). However, while the CO2 was higher than 30%, it showed a negative impact on cell growth. A mixotrophic cultivation with 3 g/l of glycerol can achieve 0.38 g l−1 day−1 of the maximum biomass productivity compared with that of 0.21 g l−1 day−1 in autotrophic cultivation. Nevertheless, the lutein content of the mixotrophic cultivation was 0.08–0.1% lower than 0.2–0.25% obtained in autotrophic cultivation, which led to a lower lutein productivity of 0.36 mg l−1 day−1 in the mixotrophic batch compared with 0.44 mg l−1 day−1 obtained in the autotrophic batch. The limitation of cell growth in the mixotrophic cultivation would be the contributing factor regarding the lower lutein productivity. The mixotrophic cultivation of repeated batch to remove potential inhibitive metabolic products from glycerol catabolism does not show an obvious improvement on biomass. Conclusively, mixotrophic cultivation achieves higher biomass productivity with lower lutein content than that of autotrophic cultivation, which leads to lower lutein productivity. Therefore, the autotrophic cultivation is preferred in the lutein production.