Gilmar A. F. Lemes^1,, João S. Yunes²

In the Lagoa dos Patos Estuary, southern Brazil, toxic blooms of cyanobacteria have been recorded for many years. Among the species of cyanobacteria that occur in the estuary Microcystis aeruginosa produces the toxin [D-Leu¹] microcystin-LR, one of the most toxic known variants. The strain Microcystis aeruginosa RST9501 was cultivated in Cyanobacteria and Phycotoxins Lab of the Oceanography Institute of the Federal University of Rio Grande - FURG and it was used for toxin extraction and purification. Sediment samples were collected from the estuary and used in the toxin degradation experiments. The decrease of toxin concentration was checked by HPLC and the results were compared with other available data. This study revealed the decreased of toxin [D-Leu¹] microcystin-LR concentration of 5µg.mL^-1 after six days, and also describes a comparative analysis of the biodegradation by the sediment and with a bacterium isolated from the collected sediment samples. It was suggested that the reduction in toxin concentration is mainly due the biodegradation by the bacterial community of Lagoa dos Patos Estuary present in the sediment. This confirms the potential of this technique as a complementary tool for biotechnological processes to remove toxins in water. It was also carried out a comparative analysis of the biodegradation of the toxin with sediment and biodegradation with an isolated bacteria from this sediment.

bacteria, biodegradation, cyanobacteria, sediment, microcystin, comparative analysis