Effect of nitrogen source on the growth, lipid, and valuable carotenoid production in the green microalga Chromochloris zofingiensis

Chromochloris (Chlorella) zofingiensis (Dönz) Fucíková & Lewis is a carotenogenic chlorophyte producing valuable carotenoids such as astaxanthin and canthaxanthin. Due to a high culture robustness, it has a potential to become a major biotechnological source of natural carotenoid pigments in the nearest future. To the best of our knowledge, this is the first report on the comparative assessment of the biomass, carotenoid, and lipid productivity of C. zofingiensis monoculture under the condition of the two-stage batch cultivation with acetate supplementation. The results proved the feasibility of complete replacement of sodium nitrate by urea in the nutrient medium for C. zofingiensis. Carotenoids (0.3% of dry cell weight) and their composition, as well as the cell lipids and their fatty acid profile, were not affected significantly during the cultivation on urea-containing media as compared to the cultivation on standard media containing nitrate. The carotenoid profile of C. zofingiensis was dominated by the valuable ketocarotenoids astaxanthin, canthaxanthin, and adonixanthin. Furthermore, the use of urea as the sole N source increased the gross yield of lipids by 30.6% as compared to that achieved on the nitrate-based medium. The fatty acid composition of the resulting lipids was compatible with the current European biodiesel standard. The cost efficiency of C. zofingiensis cultivation can be increased by replacing nitrate with urea.