European Journal of Biomedical and Pharmaceutical Sciences

EFFECT OF ANIONIC FLOCCULANT AND PH CHANGE ON THE FLOCCULATION EFFICIENCY OF PARACHLORELLA KESSLERI

Youssef Mir* and Sadki Issam

ABSTRACT

Microalgae have shown a great potential in the biotechnology field, however, high production costs have limited industrial applications. Biomass harvest is one of the major difficulties in microalgae cultivation due to high energy inputs which are needed to separate the cells from culture broth. Flocculation is considered to be a reliable method to improve cost-effectiveness in the down streaming processing. The effects of flocculation efficiency on harvesting Parachlorella Kessleri cultivated in 24 l photobioreactor were investigated by changing culture medium pH value and adding polyacrylamide flocculant (Magnafloc® 10). The flocculation experiments were conducted in 40 ml test tubes using culture broth obtained from the photobioreactor. The flocculation efficiency was evaluated by comparing the remaining cell density in the supernatant with the cell concentration before flocculation. The flocculation efficiency of 90 and 79% was obtained without flocculants and conducted under dark conditions for 24 hrs at 22ºC and 4ºC, respectively. For only 4 hrs settling time, 80% of flocculation efficiency was achieved by adjusting the culture pH to 10 using sodium hydroxide (NaOH) and adding Magnafloc® 10. By adjusting only pH value of the culture medium to 4 using Hydrogen Chloride (HCl), the measured flocculation efficiency was 97%. The addition of Magnafloc® 10 improved cell viability and slightly increase the flocculation efficiency. The anionic flocculant is only efficient when the pH of the cell culture was adjusted to a pre-defined value that induces cells immobilization and surface charge neutralization preceding flocculation process.

Keywords: Flocculation, microalgae, Parachlorella Kessleri, pH, anionic flocculant.