Harvesting Chlorella minutissima using cell coagulants

Twelve salts were tested for their ability to coagulate microalgae cells in cultures of Chlorella minutissima. The final aim was to develop an easy and efficient approach for harvesting microalgae biomass in dense cultures. Aluminum, ferric, and zinc salts coagulated C. minutissima cultures, while optimum concentration was 0.75 and 0.5 g L-1 for sulfate and chloride salts, respectively. Aluminum salts were most efficient, but caused some cell lysis, which may render this approach inappropriate in some cases. Ferric and zinc salts were ranked second and third, respectively, according to their culture cell-coagulation efficiency. Ferric salts caused a change in the color of the cells, mainly at concentrations higher than 1 g L-1. Zinc salts were less harmful for the microalgal cells, but an additional problem was observed with cell aggregates adhering to the walls of the glass test tubes. Selection of the appropriate coagulant is related to the purpose of the coagulation process.