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This study investigated the growth rate of chitosanimmobilized cells of the marine cyanobacterium Synechococcus elongatus and its potential application in the removal of nitrogen and phosphorus for wastewater treatment. Immobilized cell cultures had a lag phase of growth due to the immobilization method, and their growth rate was similar to that of free-living cell cultures. Ammonia removal was higher in free cells (54%) than in immobilized cells (29%), but nitrate removal was similar in immobilized (38%) and free cells (44%); phosphorus removal was more efficient in free cells (88%) than in immobilized cells (77%). Chlorophyll a and protein content were higher in immobilized cells. Our study demonstrates that S. elongatus immobilized into chitosan capsules can remove nutrients and is able to maintain a growth rate comparable to that of free cells in culture.

The antibiotic activity of organic extracts from cultures of six species of phytoplankton, Synechococcus elongatus, Synechocystis sp., Amphiprora paludosa, Porphyridium cruentum, Chaetoceros muelleri and Dunaliella tertiolecta was examined. The bacteria used were Gram(-) strains, Escherichia coli, Pseudomonas aeruginosa, and Klebsiella pneumoniae, and the Gram(+) strains were Bacillus subtilis, Staphylococcus aureus, and Microccocus luteus. All extracts inhibited the growth of B. subtilis and effected the generation of inhibition halos, ranging in diameter from 7.06 to 15.23 mm, for several bacteria species. Wide-spectrum antibacterial activity was observed in extracts from S. elongatus, Synechocystis sp., A. paludosa, P. cruentum, and C. muelleri. Thus, this five phytoplankton species can be used to control bacteria.

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