Flocculation of microalgae using cationic starch

Abstract

Due to their small size and low concentration in the culture medium, cost-efficient harvesting of microalgae is a major challenge. We evaluated the potential of cationic starch as a flocculant for harvesting microalgae using jar test experiments. Cationic starch was an efficient flocculant for freshwater (Parachlorella, Scenedesmus) but not for marine microalgae (Phaeodactylum, Nannochloropsis). At high cationic starch doses, dispersion restabilization was observed. The required cationic starch dose to induce flocculation increased linearly with the initial algal biomass concentration. Of the two commercial cationic starch flocculants tested, Greenfloc 120 (used in wastewater treatment) was more efficient than Cargill C*Bond HR 35.849 (used in paper manufacturing). For flocculation of Parachlorella using Greenfloc 120, the cationic starch to algal biomass ratio required to flocculate 80% of algal biomass was 0.1. For Scenedesmus, a lower dose was required (ratio 0.03). Flocculation of Parachlorella using Greenfloc 120 was independent of pH in the pH range of 5 to 10. Measurements of the maximum quantum yield of PSII suggest that Greenfloc 120 cationic starch was not toxic to Parachlorella. Cationic starch may be used as an efficient, nontoxic, cost-effective, and widely available flocculant for harvesting microalgal biomass.

A biorefinery for Nannochloropsis: Induction, harvesting, and extraction of EPA-rich oil and high-value protein

“…On the other hand, bioflocculants include biopolymers like chitosan, which comes from the deactylation of chitin from crab and shrimp shells (Farid et al, 2013;Şirin et al, 2013) and poly (γ-glutamic acid), an extracellular product from Bacillus subtilis (Zheng et al, 2012). Modern techniques involve creating new materials like nanoparticles (Farid et al, 2013), magnetic particles (Hu et al, 2013;Prochazkova et al, 2013), cationic polymers (Roselet et al, 2016;Vandamme et al, 2010), polymer composites (Hena et al, 2016), and even combinations of these materials (Hu et al, 2014). Table 3 provides a summary of the different flocculants used for harvesting Nannochloropsis.…”

Moringa oleifera SEED DERIVATIVES AS POTENTIAL BIO-COAGULANT FOR MICROALGAE Chlorella Sp. HARVESTING

“…In this study, the addition of coagulant dosage reduce the zeta potential of the microalgae colloidal and increased the biomass recovery percentage. On the other hand, the usage of non-toxic organic polymer, such as polyacrylamide copolymers, chitosan, and cationic starch have been intensively investigated for large-scale applications [18,19]. Unfortunately, they are not economical for microalgae due to its higher price.…”

Current Status and Outlook in the Application of Microalgae in Biodiesel Production and Environmental Protection

“…However, the referred inorganic multivalent metal salts are toxic and expensive when commercial-scale culture of microalgae. The non-toxic organic polymer, such as polyacrylamide copolymers, chitosan, and cationic starch (Oh et al, 2001;Vandamme et al, 2010), have been intensively investigated for large-scale applications, but they are not economical for microalgae due to its higher price. The flocculant residuals in both algal biomass and harvested water are not only negative for later processing but also disadvantages for culture medium recycling.…”