ORIGINAL PAPER Laccase and polyphenol oxidase activities of marine cyanobacteria: a study with Poly R-478 decolourization Swaminathan Palanisami Æ Sushanta Kumar Saha Æ Uma Lakshmanan Received: 3 February 2009 / Accepted: 30 July 2009 / Published online: 12 August 2009 Ó Springer Science+Business Media B.V. 2009 Abstract The various marine cyanobacterial strains tes- ted showed wide variation in growth patterns and deco- lourization patterns of the lignin model polymeric dye Poly R-478. The study revealed the presence of laccases (LACs) and polyphenol oxidases (PPOs) in marine cyanobacteria. All the ten tested strains were found to possess constitutive PPOs, whereas only four strains showed the presence of constitutive laccases. Within 7 days of incubation the highest percentage of decolourization was shown by Pho- rmidium valderianum BDU140441 (65%), and Oscillatoria chlorina BDU 140691 (12%) showed the least. Isoforms of LACs were found to be induced by the laccase elicitors veratryl aldehyde, caffeic acid, guaiacol and tannic acid. Cyanobacterial strains that possess both LACs and PPOs were relatively more efficient in decolourizing the dye. Altering the concentrations of nitrogen, phosphorus, potassium and sulphur from the basal medium influenced the efficiency of dye decolourization. Keywords Cyanobacteria Á Dye degradation Á Elicitors Á Laccase Á Poly R-478 Á Polyphenol oxidase Introduction Recalcitrant synthetic dyes and various aromatic com- pounds are the important causes for environmental pollution, which poses a challenge to the environmental biologists. Bioremediation by microorganisms, an eco- friendly method, would be the best choice to combat the pollution caused by these hazardous materials. Many studies have proved the efficacy of fungi in degrading and decolorizing synthetic dyes, and this ability was found out to be due to the production of enzymes, especially laccases (EC 1.10.3.2) (LACs) and polyphenol oxidases (EC 1.10.3.1) (PPOs), by fungi (Eggert et al. 1996; Soares et al. 2001; Dirk et al. 2003; Martinez et al. 2005). Both LACs and PPOs are copper-containing oxidases with structural difference in their copper-binding sites (McGuirl and Dooley 1999), and are distinguished by their catalytic actions; LAC catalyzes the oxidation of both ortho- and para-diphenols, whereas PPO reacts only with ortho- diphenols (Carunchio et al. 2001). In fungi, the activities of LACs and PPOs were found to increase in response to copper and aromatic and phenolic substances (Koroljova- Skorobogatko et al. 1998). Bacterial laccases were only discovered 10 years ago and their actual functions are hardly understood so far. The role of bacterial blue multi- copper proteins in different cellular processes, like sporu- lation (Kim et al. 2001)(Bacillus), resistance to copper (Wesenberg et al. 2003) (Escherichia coli) and LAC activity (Hullo et al. 2001; Solano et al. 2001; Kim et al. 2001) have been reported only recently. Cyanobacteria, the wide-adapting photo-oxygenic prokaryotes, which are self- dependent for carbon and nitrogen (certain species), have rarely been investigated for their ligninolytic activity and bioremediation ability. Till date there are no reports on ligninolytic enzymes from marine cyanobacteria except a few of our earlier investigations. Sequencing of cyano- bacterial genome (http://www.kazusa.or.jp/cyano/) showed the presence of genes for putative LAC (in Synechococcus sp. RS9917) and putative multi-copper oxidase (in various S. Palanisami (&) Á S. K. Saha Á U. Lakshmanan National Facility for Marine Cyanobacteria, Bharathidasan University, Tiruchirappalli, Tamil Nadu 620024, India e-mail: cyanobacteriologist@yahoo.com S. K. Saha Department of Biology, Texas A&M University, College Station, TX 77843-3258, USA 123 World J Microbiol Biotechnol (2010) 26:63–69 DOI 10.1007/s11274-009-0143-y