Pilot-scale production of lutein using Chlorella vulgaris

Lutein is a carotenoid pigment which has applications in the food and nutraceutical sectors, both for its use as a colourant and for its applications as a nutraceutical. Microalgae are a promising source of lutein, however to meet market demand there is a need to develop technologies which can used for large-scale production. The effect of process conditions at a 5 L scale were quantified, it was found that at low light intensities (160 mu mol photons m(-2)S(-1)) the measured specific lutein concentration was 7.4 +/- 2.1 mg g(-1) which was greater than the concentration of 3.1 +/- 1.1 mg g(-1) obtained at higher (440 mu mol photons M(-2)s(-1)) light intensities. Supplementation of the medium with nitrate led to significant increases in the maximum specific lutein concentration (10.4 +/- 5.5 mg g(-1)) compared to medium without nitrate addition (4.3 +/- 2.9 mg g(-1)). These conclusions were used to scale-up the process using 50 L bubble column photo-bioreactors, it was found that the productivity was maximised (1.6 mg L-1 day(-1)) using an air flow-rate of 1 vvm and 24 h lighting. Finally, it was found that the process could be operated on a semi-continuous basis for 32 days, achieving high lutein concentrations (15-20 mg L-1) with the performance of the system being consistent for this duration. Results from this work have clear application in the development of large-scale systems for the microalgal production of lutein.