Sustainable cultivation of Haematococcus pluvialis and Chromochloris zofingiensis for the production of astaxanthin and co-products

Large-scale cultivation of microalgae for the production of high-value compounds raises concerns on sustainability due to intense consumption of water resources. Use of wastewater for microalgae cultivation is considered a promising alternative, because it not only reduces water consumption, but also provides nutrients required for microalgae growth. In the present study, Haematococcus pluvialis and Chromochloris zofingiensis were cultivated in synthetic dairy wastewater (DWW) to identify the potential of developing high-value product first biorefineries, with astaxanthin as the main product. H. pluvialis and C. zofingiensis cultivated in DWW achieved biomass concentrations of 0.55 +/- 0.01 and 0.65 +/- 0.01 g/L, respectively. Astaxanthin contents of 2.1 +/- 0.1% and 0.4 +/- 0.1% were observed in H. pluvialis and C. zofingiensis grown in DWW. Minimum freshwater consumption for cultivation was 69.93 L/g(astaxanthin) in control growth media, which could be eliminated by cultivation of microalgae in DWW. COD, TN, and TP removal efficiencies were in the range of 94%-96%, 79%-81%, and 57%-79%, respectively, indicating capability for simultaneous biomass production and phycoremediation. Presence of carbohydrates and lipids in residual biomass suggested the applicability as feedstock for biorefining. Potential avenues to integrate wastewater treatment, astaxanthin production, and valorization of residual biomass were discussed in context of high-value product first biorefineries.