Phenolic removal in olive oil mill wastewater using loofah-immobilized Phanerochaete chrysosporium M. Ahmadi, F. Vahabzadeh*, B. Bonakdarpour, M. Mehranian and E. Mofarrah Food Process Engineering and Biotechnology Research Center, Department of Chemical Engineering, Amirkabir University of Technology (Tehran Polytechnic), Tehran, Iran *Author for correspondence: Tel.: +98-21-64543161, Fax: +98-21-6405847, E-mail: far@aut.ac.ir Received 13 April 2005; accepted 21 June 2005 Keywords: COD, decolorization, fungal cell immobilization, loofah sponge, olive oil mill wastewater, Phanerochaete chrysosporium, phenolic removal Summary Olive oil mill wastewater (OMW) has a high organic load, and this is a serious concern of the olive industry. Conventional biological wastewater treatments, despite their simplicity and suitable performance are ineffective for OMW treatment since phenolics possess antimicrobial activity. In order to carry out a proper treatment of OMW, use of a microorganism able to degrade the phenolics is thus necessary. In this study the ability of Phanerochaete chrysosporium to degrade the phenolic compounds of OMW and to decrease the chemical oxygen demand (COD) using cells immobilized on loofah was examined. The basal mineral salt solution along with glucose, ammonium sulfate and yeast extract was used to dilute the OMW appropriately. The fungus did not grow on the concentrated OMW. The extent of removal in this bio-treatment, of total phenols (TP) and the COD were 90 and 50%, respectively, while the color and aromaticity decreased by 60 and 95%, respectively. The kinetic behavior of the loofah-immobilized fungus was found to follow the Monod equation. The maximum growth rate l max was 0.045 h )1 while the Monod constant based on the consumed TP and COD were (mg/l) 370 and 6900, respectively. Introduction Annual global production of olive oil is about 1.6 mil- lion tons (Perez et al. 1998). In the olive oil extraction process and along with the oil which accounts for 20% of the total, two main by-products are produced: a solid residue and a black colored wastewater contributing 30 and 50% of the total, respectively (Perez et al. 1998). The amount of the wastewater produced (olive oil mill wastewater, OMW) varies depending on the method used for the oil extraction: the classical press method produces 0.5–0.8 m 3 /ton of olives processed while this figure for the more recent three-phase centrifugation system is 1 m 3 /ton of olives (Perez et al. 1998). The serious problem for olive oil industry is to find a proper method to either dispose of and/or treat OMW, without creating environmental problems. The presence of powerful pollutants in OMW shows itself by the chemical oxygen demand (COD) value, which is in the range of 80–200 g/l (Hamdi 1996). It is interesting to see the position of this value relative to that of a typical municipal sewage 200–400 times higher for OMW (Fadil et al. 2003). Despite this, the economic viability of OMW has been discussed and several feasible alterna- tives regarding the purification and exploitation of this wastewater have been proposed (Toscano et al. 2003). But there are major drawbacks for proper disposal of OMW, mainly due to the phenolics present in the waste which have antimicrobial and phytotoxic activity. Conventional biological methods are not efficient way(s) therefore, of treating OMW. For example due to inhibitory action of OMW on sludge microorganisms, the OMW must be diluted at least 70 times with tap water before use of aerobic activated sludge processes for its treatment (Hamdi 1996). In fact these character- istic properties slow the progress of the COD removal process and reduce the effluent economic viability. Se- vere limitations are introduced by OMW spreading over agricultural soils or even discharging it in rivers and waterways. Not only in the Mediterranean regions but in the other countries where olive is produced, similar situations (regarding unfriendly behavior of OMW on the environment) can be found, e.g., in Middle-Eastern countries. White rot fungi are the only microbes known to mineralize lignin and all lignin-like compounds to car- bon dioxide and water (Kirk & Farrell 1987). These fungi are among most popular microbes known to de- grade the phenolics pollutants. The degradation is cat- alyzed by a group of heme-containing oxidative enzymes which are secreted by the fungi in response to being faced with nutrient deficiency and during the secondary World Journal of Microbiology & Biotechnology (2006) 22: 119–127 Ó Springer 2005 DOI 10.1007/s11274-005-9006-3