Exopolysaccharide Production by Cyanothece sp. 81 Applied Biochemistry and Biotechnology Vol. 82, 1999 Copyright © 1999 by Humana Press Inc. All rights of any nature whatsoever reserved. 0273-2289/99/82/0081/$12.50 81 *Author to whom all correspondence and reprint requests should be addressed. Exopolysaccharide Production by a Marine Cyanobacterium Cyanothece sp. Application in Dye Removal by Its Gelation Phenomenon VISHAL SHAH, NIKKI GARG, AND DATTA MADAMWAR* Post Graduate Department of Biosciences, Sardar Patel University, Vallabh Vidyanagar, 388 120, Gujarat, India, E-mail: vish_dm@yahoo.com Received July 26, 1999; Revised November 16, 1999; Accepted November 22, 1999 Abstract Cyanobacterium Cyanothece sp. ATCC 51142 has been shown to pro- duce an exopolysaccharide (EPS) at a high level. EPS production was found to be influenced by the concentration of salt, pH, and type of nitro- gen source. Maximum polysaccharide production was found to occur at a 4.5% (w/v) NaCl salt concentration, pH 7.0, and in the presence of NaNO 3 as the nitrogen source. The gelation of EPS in alkaline conditions was employed to remove the dyes from the effluents. The effect of organic molecules and metal ions on the efficiency of dye removal capacity was investigated. A laboratory-scale reactor was prepared to treat artificial textile effluent. Index Entries: Cyanothece; cyanobacterium; dyes; exopolysaccharide; gelation; wastewater treatment. Introduction Because of the growth of industries in the last few decades, a wide variety of man-made (anthropogenic) compounds have been generated worldwide, and the production of such compounds is associated with the formation of large amounts of wastes. Although the process of industrial- ization is important for nations’ prosperity, the pollution caused by the industries cannot be neglected. With the increasing awareness for the need to protect the environment, the treatment and disposal of industrial wastes have acquired great significance.