Surface activity of biomolecules released from microalgae harvested by ozone-flotation

Abstract

This paper evaluates the relation between the efficiency of harvesting microalgae biomass or biomolecules (proteins, lipids and carbohydrates) and the surface activity of the amphiphiles released during the harvesting process. Microalgae cultivated in wastewater was evaluated using a laboratory scale ozone-flotation reactor. Applying the highest biomass concentration (1800 mg/L) and a flow ratio gas–liquid of 3, recovered 79% biomass with a maximum yield of 7.6 mg biomass/mg O 3 and a release of biomolecules greater than 70%. Adjusting surface pressures of the harvested samples to integrated Gibbs model indicated that longer ozone than 19 min exposure times caused a decrease in the hydrophobic region of the molecules. This affected the efficiency of the amphiphiles present in the sample, requiring a higher concentration (from 534.72 ± 9.63 mg/L to 1542.45 ± 5.66 mg/L) to reduce the surface tension to the minimum values obtained (45.26 ± 0.73 mN/m). In conclusion, ozone exposure needs be closely monitored to ensure effective biomass and biomolecules separation. • Harvesting of biomass and biomolecules by ozone-flotation was higher than 70%. • Integrated Gibbs model described changes in microalgae’s amphiphiles. • Longer exposure to ozone caused a decrease in biomolecules’ hydrophobic region. • Ozone exposition must be controlled to ensure separation of biomolecules.