Investigation of microalgae culture by autoflocculation methodologies

Abstract

Harvesting of microalgae from their different cultivation media has pointed out challenges in resolving the problems of flocculation. These challenges must be faced with a  suitable method for inducing flocculation that avoid or limit the microalgae’s contamination. This study developed the fundamental experiments with a support of chemicals and some bacteria strains inducing the flocculation of Chlorella vulgaris SAG 211-19.  Particularly, the determination of minimum content of Mg²⁺, Ca²⁺, E. coli ATCC 85922 and Bacillus subtilis MT300405 was effectuated with co-cultivation of microalgae and set up in batch culture in Bold’s Basal Medium. As a result, the adjustment in 25 minutes of 199.2 mg/L CaCl₂.2H₂O, 50 mg/L KH₂PO₄, and of 141 mg/L MgSO₄.7H₂O induced a microalgal settling efficiency of 81% and 70%, respectively. Meanwhile, the perfomance of microalgal removing reached up to 83.6% and 84% by the inoculation into microalgal culture media of a minimum initial cell density of 8.1 ´ 10⁵ CFU/mL of Bacillus subtilis MT300405 and 12 ´ 10⁵ CFU/mL of E. coli ATCC 85922, respectively. The flocculation of microalgal cells by bacterial inoculation did not require a high pH adjustment as in the case of salt addition.