Research paperHarvesting microalgae using ozoflotation releases surfactant proteins, facilitates biomass recovery and lipid extraction

- Proteins released during ozoflotation lower the surface tension and promote foaming.
- C-Phycocyanin beta chain was the main protein released by microalgae.
- Doses of 0.047 mg O3/mg biomass resulted in the highest amount of lipids recovered.
- Doses higher than 0.058 mg O3/mg biomass decreased the total of lipids recovered.
- The highest ozone dose tested produced the highest biomass recovery (75%).

In this paper, a mixed microalgal consortium (including cyanobacteria) was separated from treated wastewater by ozoflotation to evaluate the method's effect on protein excretion, lipids extraction, and cell recovery. Microalgae suspensions obtained from an artificial lake, Lake Nabor Carrillo, were subjected to different ozoflotation conditions (0.028-0.136 mg O3/mg biomass). During ozoflotation, proteins released exhibited surfactant activity in the water disrupting the surface tension of water to values of 42.73 mN/m. A critical micelle concentration (CMC) of at least 550 ± 17 mg protein/L was needed to produce foaming and biomass separation of the aqueous medium. The C-Phycocyanin beta chain was identified as one of the main proteins released during the ozoflotation process. Biomass recovery was found to be directly proportional to the ozone dose; best results (75% as TSS) were obtained at the highest dose used (0.14 mg O3/mg biomass). In contrast, the best lipid recovery (16% mg lipid/mg biomass) was achieved when using low ozone doses (0.047 mg O3/mg biomass).