Cocamidopropyl betaine-assisted foam separation of freshwater microalgae Desmodesmus brasiliensis

The downstream process of microalgae derived products is pinned by the harvesting/dewatering of microalgae biomass. Thus, a significant part in the industrial application of microalgae is to find a method to harvest microalgae on a large scale with a low energy cost and high financial efficiency. Foam separation technology is a simple, mild and efficient separating method based on bubbles as separating medium to separate substances of surfactivity. In this study, the cocamidopropyl betaine (CAPB), a natural surfactant, was used to harvest the freshwater microalgae Desmodesmus brasiliensis by foam separation. The paper shows when pH = 3, the recovery rate of cocamidopropyl betaine (CAPB) as surfactant (R(%) = 93.63 ± 1.75) can match the traditional surfactant CTAB, with a much larger enrichment ratio (E = 23.12 ± 0.028). Response Surface Methodology (RSM) was used to optimize the recovery rate R(%) after obtaining the optimum condition of harvesting the Desmodesmus brasiliensis and finally the optimum result of R (%) = 94.4 was reached. Compared with traditional centrifuge separation, the amount of algae lutein from Desmodesmus brasiliensis collected by foam separating was larger than that by centrifuge separation, suggesting this cheap and natural surfactant has the potential to be applied in commercial-scale microalgae biomass recovery and especially in boosting lutein yeild.