Magnetic-cationic cassava starch composite for harvesting Chlorella sp. TISTR8236

Microalgae are cultured for their useful chemicals, but their development is restricted by the costs and difficulties of harvesting them. New composites, magnetic-cationic cassava starch, were successfully developed to facilitate harvesting. Compared to naked magnetic particles, the composites exhibited higher potential for algal cell recovery. In addition, harvest capacity through the composites was positively related to the degree of cationic substitution (DS) in modified cassava starch. The application of 500 mg L−1 composites with DS value ≥ 0.76 to recover 1 g L−1Chlorella sp. TISTR8236 (1.67 ± 0.01 g-dry cell weight g-composites−1) from medium broth at pH 9.5 was significantly (p ≤ 0.005) >98% effective. The separation efficiency of this composite for 1 g L−1 algal biomass was evaluated under different composite doses (200 to 800 mg L−1) and pH levels (4 to 10). Ninety-five percent of the algal cell separation efficiency of the magnetic and 0.76 DS cationic starch composite was recorded, when applied to the 300 mg L−1 composite to harvest 1 g L−1Chlorella sp. TISTR8236 at pH 10 within 2 min. The adsorption isotherm fit the Langmuir model. In addition, desorption of algal cells was conducted by adjustment of the pH of the culture medium. The highest desorption (9.69%) was recorded at pH 12. These composite magnetic-cationic cassava starch particles were shown to be a new adsorption material for algal cell harvesting. This alternative composite for magnetic separation may represent an effective method for saving time and energy in algal industrial processing.