Effect of gradual nitrogen removal on growth, biochemical composition and fatty acid profile of microalga Haematococcus pluvialis

Different physicochemical factors influence the growth of Haematococcus pluvialis and should be assessed in order to optimal production of biomass and its chemical composition. There is few information on the effect of gradual nitrogen limitation on the microalgae.  Hence, in the present study the effects of gradual nitrogen removal from culture medium, in two stages, on growth, chlorophyll and astaxanthin content, biochemical compounds and fatty acid profile in H. pluvialis was evaluated. During 55 days culture, biomass production and chlorophyll content in the treatment group showed a significant decrease (P<0.05) compared to the control, whilst no significant change was observed in the astaxanthin content. The highest content of astaxanthin was observed before the replacement of culture medium in both experimental groups. At the end of the experiment, the content of lipid, protein, and carbohydrate in the nitrogen-free culture showed a significant decrease. Fatty acid profile showed a reduction in unsaturated fatty acid with nitrogen limitation. Overall, the results showed that the stepwise nitrogen depletion caused a change in biochemical composition of microalgae. In the same condition, as the algal cells were gradually subjected to severe stress, consequently, the production of astaxanthin was not affected.