Water Research 36 (2002) 1896–1901 Research note Biodegradation of a polymeric dye in a pulsed bed bioreactor by immobilised Phanerochaete chrysosporium I. Mielgo, M.T. Moreira, G. Feijoo, J.M. Lema* Department of Chemical Engineering, Institute of Technology, University of Santiago de Compostela, Avda. Ciencias s/n, E-15706 Santiago de Compostela, Galiza, Spain Received 21 May 2001; accepted 30 July 2001 Abstract An immobilised fungal bioreactor operated with pulsation of the gas-phase is proposed and operated at variable conditions for the continuous biological degradation of complex structures. In order to test the system, a hardly biodegradable dye (Poly R-478) was selected as a model compound and Phanerochaete chrysosporium as the ligninolytic fungus. High percentages of decolourisationFbetween 65% and 80%Funder optimal conditions were achieved. Moreover, the system proved to have high stability with long operational periods (at least, 90 days). During the operation Manganese Peroxidase was the sole ligninolytic enzyme detected which points out this enzyme as the main substance responsible for decolourisation. The optimal conditions established were the following: temperature of 371C, use of oxygen, Mn 2+ concentrations between 33 and 330 mM and exogenous H 2 O 2 added in periodical pulses (as chemical reagent, 1 mM or as H 2 O 2 enzymatically generated by 0.6UL À1 glucose oxidase and residual glucose). r 2002 Elsevier Science Ltd. All rights reserved. Keywords: Decolourisation; Dye treatment; Polyanthraquinone dye; Pulsed bed bioreactor; Immobilised Phanerochaete chrysospor- ium; Manganese Peroxidase 1. Introduction Synthetic organic colourants are used for several purposes in the textile, cosmetic, paper making, food and pharmaceutical industries [1]. Although some physical–chemical treatments have being applied for colour removal from wastewaters, these processes present high operational costs and limited applicability as main disadvantages [2]. Besides, the colourants remain unaltered in most cases and the produced sludge is, in this way, considered as a hazardous residue. Alternatives based on conventional biological processes are relatively ineffective for colour removal from industrial wastewaters [3]. White-rot fungi are well known for their outstanding ability to produce extracellular oxidative enzymes, which initiate lignin depolymerisation [4]. This degrad- ing ability has opened new prospects for the develop- ment of biotechnological processes aimed at the degradation of xenobiotic compounds [5], effluent decolourisation [3,6] and biobleaching of Kraft pulp [7]. There are few reports specifically on dye decolourisa- tion in continuous bioreactors. Yang and Yu [8] reported the decolourisation of a disperse dye (Red- 553) in a fixed-film bioreactor to percentages higher than 80%. Zhang et al. [9] also considered the continuous decolourisation of an azo dye, Orange II, in a packed- bed reactor, with a high decolourisation efficiency (97% colour removal). However, the problems encountered with the operation in both bioreactors were short fungal lifetime due to the limitation of a growth source required for ligninolytic enzyme complex activation [10] and their remarkable predisposition for branching with the *Corresponding author. Tel.: +34-981-563100; fax: +34- 981-595012. E-mail address: jmlema@usc.es (J.M. Lema). 0043-1354/02/$-see front matter r 2002 Elsevier Science Ltd. All rights reserved. PII:S0043-1354(01)00384-0