Chlamydomonas reinhardtii flocculation by metal cations and high pH with different phenotypic traits

The energy and expense required to harvest the algae might be greatly reduced by flocculating the cells first before centrifuging them. However, it is not fully known how variations in phenotypic variables, such as cell surface characteristics, cell size, and motility, affect the effectiveness of metal cations and pH-induced flocculation. Our findings show that the addition of divalent cations like calcium and magnesium (>5 mM) causes both wild-type and cell wall-deficient strains of the green unicellular alga Chlamydomonas reinhardtii to flocculate effectively (>90%) at an elevated pH of the medium (pH 11). Under weakly alkaline circumstances (pH 8.5), the trivalent ferric cation (at 10 mM) was found to be crucial for promoting flocculation, with a maximum efficiency exceeding 95% and 85% for wild-type CC1690. A pH of >11 and a calcium concentration of 5 mM could be used to achieve nearly full flocculation, and the medium that was recovered after cell removal could be recycled without altering algal growth rates. Additionally, the effectiveness of flocculation was not significantly affected by the lack of starch in the cell. These discoveries advance our knowledge of flocculation in several Chlamydomonas strains and have implications for low-cost techniques for collecting algae with various phenotypic characteristics. It will be possible to develop low-cost methods for harvesting cell biomass with the aid of additional study on the conditions (such as pH and metal ions) required for efficient flocculation of various algal groups with various properties, both at small and large scales