Evaluation of sodium tripolyphosphate-alginate coating and re-calcifying on the entrapment of microalgae in alginate beads

Coating with polymers and re-calcifying have been done to retard the liberation of immobilized cells. Considering that sodium tripolyphosphate (TPP) is highly effective for chelating calcium ions, it is possible to postulate that if a layer of TPP is deposited over calcium alginate beads, the strong interaction between TPP ions and calcium may help in improving their cell holding capacity. In this study, we evaluate and compare the efficiency of cell entrapment between beads of alginate-immobilized microalgae Chlorella vulgaris, Acutodesmus (Scenedesmus) obliquus, and Synechococcus elongatus that were re-calcified, with those that were coated with varying ratios of alginate:TPP. Results indicate that re-calcifying and coating do not limit the growth of the species studied. For C. vulgaris and A. obliquus, coating is more efficient for cell entrapment than re-calcifying. In contrast, for S. elongatus, re-calcifying is more effective than coating, suggesting a relationship between the cell size and the efficiency of cell entrapment.