Production of vitamin D3 in Nannochloropsis oceanica by post-cultivation UVB exposure: Effect of dose, culture density, and cultivation conditions

The microalga Nannochloropsis oceanica presents a promising source of non-animal vitamin D 3 , produced when exposed to UVB radiation. This study aimed to test and optimize a post-cultivation UVB treatment for production of vitamin D 3 in N. oceanica . The study further investigated the importance of different cultivation conditions for vitamin D 3 production. The UVB treatment successfully initiated production of vitamin D 3 , resulting in biomass with 0.218 μg·g −1 DM after 30 min of UVB exposure. With the current setup, a saturation limit was reached after 100–120 min, irrespective of the culture density. Such plateau effect may restrict the obtainable amount of vitamin D 3 using this approach. The used cultivation temperature proved highly influential, with production of vitamin D 3 being 2.7-fold higher in biomass produced at low temperature. In combination, these results strengthen the potential of N. oceanica as a future source of vitamin D 3 and provide a framework for further concept development. • Vitamin D 3 produced in N. oceanica by post-cultivation UVB exposure • Biomass containing up to 0.260 μg vitamin D 3 ·g −1 DM achieved • No side effect on polyunsaturated fatty acids, including EPA • Low cultivation temperature improved subsequent vitamin D 3 production.