Biotransformation of indigo carmine to isatin sulfonic acid by lyophilized mycelia from Trametes versicolor

Indigo carmine (IC) was biotrasformed to 5-isatinsulfonic acid using intracellular and associated enzymes from Trametes versicolor lyophilized mycelia; even when extracellular enzymes were absent, in high concentration solutions of IC (4 000 mg L-1) and non-sterile condition. T. versicolor was grown in wheat strew and malt extract liquid medium and harvested during the stationary growth phase, it was lyophilized and made to react with indigo carmine. Experimental series were performed at different IC concentrations (from 100 to 4000 mg L-1). Color removal was 99.90, 98.75, 88.35, 79.47, 70.0 and 40.35% for 100, 500, 1000, 2000, 3000 and 4000 mg L-1 of IC, respectively after 120 h with exception for 100 mg L-1 of IC, which reached total color removal after 1 h. Reacted mixture byproducts were separated by column chromatography. IC biotransformation to 5-isatinsulfonic acid was confirmed by HPLC, UV-VIS, FT- IR, 1H and 13C NMR spectroscopy. Activity of laccase from lyophilized mycelia was conserved after one year at 4°C. Dehydrated biological material in colorant biodegradation is a new method which allows obtaining high discoloration efficiencies. Lyophilized mycelia could be more stable than traditionally used wet biomass or liquid culture for biodegradation of color dye.Key words: Biodegradation, indigo carmine, Trametes versicolor

Removal of hexavalent chromium of contaminated soil by coupling electrokinetic remediation and permeable reactive biobarriers

PURPOSE: In this study, a novel and ecological alternative have been developed to treat soils contaminated with hexavalent chromium coupling two well-known systems: electrokinetic remediation and permeable reactive biobarriers. The electric field promotes the electromigration of the hexavalent chromium oxyanions towards the anode. The biobarriers were placed before the anode electrode, in order to promote the reduction and retention of the chromium migrating in its direction. Thus, this technology provided a global treatment to soil removal without subsequent treatments of the contaminated effluents. METHODS: The electrokinetic system was coupled with two different permeable reactive biobarriers composed by Arthrobacter viscosus bacteria, supported either in activated carbon or zeolite. An electric field of 10 V was applied and two different treatment times of 9 and 18 days were tested. RESULTS: Removal values of 60% and 79% were obtained when electrokinetic treatment was coupled with zeolite and activated carbon biobarriers, respectively, for a test period of 18 day. The reduction of hexavalent chromium to trivalent chromium was around 45% for both systems. CONCLUSIONS: In this work, two types of biobarriers were efficiently coupled to electrokinetic treatment to decontaminate soil with Cr(VI). Furthermore, the viability of the new coupling technology developed (electrokinetic + biobarriers) to treat low-permeability polluted soils was demonstrated.This work was supported by the Spanish Ministry of Science and Innovation (CTQ2008-03059/PPQ), Xunta de Galicia (08MDS034314PR). The authors are grateful to the Spanish Ministry of Science and Innovation for providing financial support for Marta Pazos under the Ramon y Cajal program and the Fundacao para a Ciencia e Tecnologia, Ministerio da Ciencia e Tecnologia, Portugal through the PhD grant of Bruna Fonseca (SFRH/BD/27780/2006)