Efficient Harvesting of Nannochloropsis Microalgae via Optimized Chitosan-Mediated Flocculation

Elvis T Chua; Eladl Eltanahy; Heejae Jung; Manuel Uy; Skye R Thomas-Hall; Peer M Schenk

doi:10.1002/gch2.201800038

Efficient Harvesting of Nannochloropsis Microalgae via Optimized Chitosan-Mediated Flocculation

Glob Chall. 2018 Sep 21;3(1):1800038. doi: 10.1002/gch2.201800038. eCollection 2019 Jan.

Authors

Elvis T Chua¹, Eladl Eltanahy^{1

2}, Heejae Jung¹, Manuel Uy³, Skye R Thomas-Hall¹, Peer M Schenk¹

Affiliations

¹ Algae Biotechnology Group School of Agriculture and Food Sciences The University of Queensland Brisbane Queensland 4072 Australia.
² Algae Laboratory Botany Department Faculty of Science Mansoura University Mansoura 35516 Egypt.
³ The Johns Hopkins University Applied Physics Laboratory Laurel Maryland 20723 USA.

Abstract

Food-grade rather than synthetic or chemical flocculants are needed for microalgae harvesting by settling, if used for food products. Chitosan is effective in harvesting freshwater microalgae, but it is expensive and typically not suitable for marine microalgae like Nannochloropsis. To minimize costs for food-grade flocculation, a number of potentially important parameters are considered, including chitosan solubility and optimized chitosan-mediated flocculation of Nannochloropsis sp. BR2 by a five-factor central composite design experiment. Results show that an optical density (440 nm) of 2 (0.23 g dry weight L^-1), initial pH of 6, final pH of 10, and 22 ppm chitosan with a viscosity of 1808 cP provide optimum flocculation efficiency, which is predicted to be in the range of 97.01% to 99.93%. These predictions are verified on 4.5 and 8 L Nannochloropsis sp. BR2 cultures.

Keywords: Nannochloropsis; central composite design; chitosan; flocculation; microalgae harvesting.