Photoautotrophic, mixotrophic, and heterotrophic culture media optimization for enhanced microalgae production

Several photoautotrophic microalgae can bear machinery for enhanced utilization of externally added sugars under mixotrophic and heterotrophic conditions. Literatures on microalgae have reported numerous standard media which might be adequate for lab scale studies but not for the concentrated production at industrial scale due to poor biomass and lipid productivities. An optimized medium fortified with all essential nutrients is vital to produce concentrated microalgae biomass along with high lipid content. The present study is presenting the development of optimized media by using the Box-Behnken statistical design method for the enhanced biomass of Arthrospira platensis, Nannochloropsis sp. and Spirulina sp. cultivated under photoautotrophic, mixotrophic and heterotrophic conditions. All the nine optimization models were significant and exhibited quite high coefficient of multiple determination, R2 greater than 0.987 showing the applicability of the generated models. Mixotrophic optimized media of each microalgae resulted in maxima of biomass and lipid in comparison to that of other two cultivation conditions media. Maximum biomass productivity of A. platensis, Nannochloropsis sp. and Spirulina sp. was 7.23 g/L/d, 6.01 g/L/d, and 7.69 g/L/d, respectively in respective mixotrophic optimized media. Proper balance of carbon, nitrogen and vitamins in the media induced lipid up to 77 % of cell biomass. The productivities of both biomass and lipid achieved using mixotrophic optimized media in batch are many folds higher than that obtained in standard cultivation media. Results obtained from batch operation ensures that mixotrophic optimized media would trigger the microalgae production if employed with appropriate feeding strategy in fed batch or continuous operation.