Journal of Chemical Technology and Biotechnology J Chem Technol Biotechnol 82:399–406 (2007) Decolourisation and treatment of pulp and paper mill effluent by lignin-degrading Bacillus sp. Abhay Raj, MM Krishna Reddy and Ram Chandra ∗ Industrial Toxicology Research Centre, Lucknow, India Abstract: Three lignin-degrading bacterial strains, identified as Paenibacillus sp., Aneurinibacillus aneurinilyticus and Bacillus sp. have been examined for the treatment of pulp and paper mill effluent. The results of this study revealed that all three bacterial strains effectively reduced colour (39–61%), lignin (28–53%), biochemical oxygen demand (BOD) (65–82%), chemical oxygen demand (COD) (52–78%) and total phenol (64–77%) within six days of incubation. However, the highest reduction in colour (61%), lignin (53%), BOD (82%) and COD (78%) was recorded by Bacillus sp. while, maximum reduction in total phenol (77%) was recorded with Paenibacillus sp. treatment. Significant reduction in colour and lignin content by these bacterial strains was observed after two days of incubation, indicating that bacterium initially utilized growth supportive substrates and subsequently chromophoric compounds thereby reducing lignin content and colour in the effluent. The total ion chromatograph (TIC) of compounds present in the ethyl acetate extract of control and bacterial treated samples revealed the formation of several lignin-related aromatic compounds. The compounds identified in extracts of treated samples by Paenibacillus sp were t-cinnamic acid and ferulic acid, while 3-hydroxy-4-methoxyphenol, vanillic acid and vanillin acid by A. aneurinilyticus and gallic acid and ferulic acid by Bacillus sp. respectively indicating the degradation of lignin present in the effluent. The identified compounds obtained after different bacterial treatments were found to be strain-specific. Among these identified compounds, ferulic acid, vanillic acid and vanillin could have immense value for their use in preservatives and in the food flavour industry.  2007 Society of Chemical Industry Keywords: pulp paper effluent; bacterial treatment; Bacillus sp.; lignin-related aromatic compounds; GC-MS INTRODUCTION Pulp and paper milling are major industrial sectors using a huge amount of lignocellulosic raw materials and water during manufacturing processes, and releasing chlorinated lignosulphonic acid, chlorinated resin, chlorinated phenol and chlorinated hydrocarbon in the effluent. 1 The generation of wastewater and the characteristics of pulp and paper mill effluent depend upon the type of manufacturing process adopted and the extent of recycling of water employed in the plant. Due to the high chemical diversity of the organic pollutants in paper and pulp mill process water, a wide variety of toxic effects on aquatic communities in recipient watercourses have been observed. 2 Discharge of untreated effluent from the pulp and paper industry causes slime growth, thermal impacts, scum formation, colour problems, and loss of aesthetic beauty in the environment. They also increase the amount of toxic substances in the water, causing death to the zooplankton and fish, as well as profoundly affecting the terrestrial ecosystem. 3 The treatment methods adopted in industry, such as aerated lagoon and activated sludge processes, are usually able to remove 85–90% of the readily biodegradable fraction of the biochemical oxygen demand (BOD) from these effluents. However, these systems are generally less effective in the removal of colour, chemical oxygen demand (COD) and chlorinated phenolic compounds. 4 Colour in pulp and paper mill effluent is due to lignin and its derivatives, which not only causes serious aesthetic problems but also inhibits natural photosynthesis in streams due to the absorbance of sunlight. 5 Further, lignin and its derivatives lead to a chain of adverse effects on the aquatic ecosystem, as the growth of primary as well as secondary and tertiary consumers are adversely affected. 6 On the other hand chlorinated organic compounds have become a matter of great concern due to their recalcitrance to biological degradation, toxicity (acute and chronic) and potential to accumulate in aquatic organisms. 2 A significant number of organic compounds present in the pulp and paper mill effluent have been classified as carcinogenic, mutagenic and clastogenic, 7,2 and endocrinic. 8 Physico-chemical treatment methods such as incin- eration of black liquor lignin, 9 UV/TiO2 oxidation systems, 10 Fenton and photo-Fenton reactions, 11 and chemical coagulation of lignin using synthetic and natural coagulants, 12 have been reported for effec- tive reduction in colour and toxicity of pulp and ∗ Correspondence to: Ram Chandra, Environmental Microbiology Section, Industrial Toxicology Research Centre, M.G. Marg, Post Box No. 80. Lucknow -226 001 India E-mail: chandra microbio@indiatimes.com (Received 14 December 2006; revised version received 25 January 2007; accepted 27 January 2007) DOI: 10.1002/jctb.1683  2007 Society of Chemical Industry. J Chem Technol Biotechnol 0268–2575/2007/$30.00