Effective Harvesting of Nannochloropsis Microalgae Using Mushroom Chitosan: A Pilot-Scale Study

Elvis T Chua; Ajam Y Shekh; Eladl Eltanahy; Skye R Thomas-Hall; Peer M Schenk

doi:10.3389/fbioe.2020.00771

Effective Harvesting of Nannochloropsis Microalgae Using Mushroom Chitosan: A Pilot-Scale Study

Front Bioeng Biotechnol. 2020 Jul 14:8:771. doi: 10.3389/fbioe.2020.00771. eCollection 2020.

Authors

Elvis T Chua¹, Ajam Y Shekh^{1

2}, Eladl Eltanahy³, Skye R Thomas-Hall¹, Peer M Schenk¹

Affiliations

¹ Algae Biotechnology Laboratory, School of Agriculture and Food Sciences, The University of Queensland, Brisbane, QLD, Australia.
² Plant Cell Biotechnology Department, CSIR-Central Food Technological Research Institute, Mysore, India.
³ Algae Laboratory, Botany Department, Faculty of Science, Mansoura University, Mansoura, Egypt.

Abstract

For efficient downstream processing, harvesting remains as one of the challenges in producing Nannochloropsis biomass, a microalga with high-value omega-3 oils. Flocculation is an effective, low-energy, low-cost method to harvest microalgae. Chitosan has been shown to be an effective food-grade flocculant; however, commercial chitosan is sourced from crustaceans, which has disadvantages including concerns over heavy-metal contamination. Thus, this study tests the flocculation potential of mushroom chitosan. Our results indicate a 13% yield of chitosan from mushroom. The identity of the prepared chitosan was confirmed by Fourier-transform infrared (FTIR) spectroscopy. Furthermore, results show that mushroom chitosan can be an alternative flocculant with >95% flocculation efficiency when tested in 100-mL jar and 200-L vertical column photobioreactor. Applications in a 2000-L raceway pond demonstrated that thorough mixing of mushroom chitosan with the algal culture is required to achieve efficient flocculation. With proper mixing, mushroom chitosan can be used to produce food-grade Nannochloropsis biomass suitable for the production of vegan omega-3 oils as a fish oil alternative.

Keywords: Nannochloropsis; chitosan; flocculation; harvesting; mushroom; omega-3; vegan.