Biotransformation of Malachite Green by the FungusCunninghamella elegans

Abstract

The filamentous fungus Cunninghamella elegans ATCC 36112 metabolized the triphenylmethane dye malachite green with a first-order rate constant of 0.029 mol h ؊1 (mg of cells) ؊1 . Malachite green was enzymatically reduced to leucomalachite green and also converted to N-demethylated and N-oxidized metabolites, including primary and secondary arylamines. Inhibition studies suggested that the cytochrome P450 system mediated both the reduction and the N-demethylation reactions.Malachite green, an N-methylated diaminotriphenylmethane dye, has been widely used as the most efficacious antifungal agent in the fish farming industry (26). It is also used extensively in textile industries for dyeing nylon, wool, silk, leather, and cotton (10). Although malachite green is not approved by the U.S. Food and Drug Administration, its worldwide use in aquaculture will probably continue due to its relatively low cost, ready availability, and efficacy (26); therefore, potential human exposure to malachite green could result from the consumption of treated fish (2) and from working in the dye and aquaculture industries. Malachite green is highly toxic to mammalian cells; it promotes hepatic tumor formation in rodents and also causes reproductive abnormalities in rabbits and fish (13,24). The structural similarity of malachite green to other carcinogenic triphenylmethane dyes also raises suspicion of carcinogenicity; gentian violet (crystal violet) is a thyroid and liver carcinogen in rodents (17), and pararosaniline is a bladder carcinogen in humans (7). Based on the potential for adverse human health effects, the U.S. Food and Drug Administration nominated malachite green as a priority chemical for carcinogenicity testing by the National Toxicology Program in 1993 (10). These studies are presently being conducted at the National Center for Toxicological Research, Jefferson, Ark.From an environmental standpoint, there is concern about the fate of malachite green and its reduced form, leucomalachite green, in aquatic and terrestrial ecosystems, since they occur as contaminants (6, 21) and are potential human health hazards. Studies on the biodegradation of triphenylmethane dyes have focused primarily on the decolorization of dyes via reduction reactions (4,19,22,23,25). Intestinal microflora were shown to reduce crystal violet (18) and malachite green (16) to their respective leuco derivatives. The fungal metabolism of these compounds was first reported by Bumpus and Brock (5). The white rot fungus Phanerochaete chrysosporium, grown under ligninolytic conditions, was shown to metabolize crystal violet to three metabolites by sequential N demethylation of the parent compound, which was catalyzed by lignin peroxidase. They also reported (5) that nonligninolytic cultures of P. chrysosporium could also degrade crystal violet, although the N-demethylation products were not found under nonligninolytic conditions, suggesting that another mechanism for degrading crystal violet existed in this fungus. The present study was conducted to deter...

Characterization of a broad-specificity non-haem iron N-demethylase from Pseudomonas putida CBB5 capable of utilizing several purine alkaloids as sole carbon and nitrogen source

“…To our knowledge, the P. putida CBB5 methylxanthine Ndm provides the first concrete example of a Rieske non-haem iron oxygenase with broadbased N-demethylase activity on a number of purine alkaloids. N-Demethylation (or N-dealkylation) reactions in eukaryotes and prokaryotes are known to be catalysed only by cytochrome P450s (Abel et al, 2003;Asha & Vidyavathi, 2009;Caubet et al, 2004;Cha et al, 2001;Guengerich, 2001;Tassaneeyakul et al, 1994), various flavo-enzymes (Chang et al, 2007;Kvalnes-Krick & Jorns, 1986;Meskys et al, 2001;Nishiya & Imanaka, 1993;Phillips et al, 1998;Shi et al, 2004;Wagner, 1982) and a ketoglutarate-dependent non-haem iron oxygenase (Tsukada et al, 2006). This study therefore broadens our understanding of the possible enzymic mechanism for N-demethylation and will aid the discovery of new microbial N-demethylases in the future.…”

Distribution and depuration of the potentially carcinogenic malachite green in tissues of three freshwater farmed Chinese fish with different food habits

“…The use of MG in fish farming is prohibited in the United States and the European Union (EU) due to its toxicological and potentially carcinogenic nature (Culp and Beland, 1996;Srivastava et al, 2004). However, MG is often illegally used by the fish farming industry due to its low cost, easy availability, and high efficacy against fungus, bacteria and parasite (Cha et al, 2001). Findings of MG residues in aquaculture products have frequently been reported in Rapid Alert System for Food and Feed (RASFF) notifications of the European Commission.…”

Biotransformation of Vincamine using Microbial cultures

“…The UV λ max of the metabolites were within a narrow range with that of vincamine which indicates that their extinction coefficient at 270nm was not significantly different from that of the parent drug. Cha reported that the fungi Cunninghamella elegans was able to N-demethylate malachite green, where the metabolites showed a slight decrease (618 to 608nm) in absorption maxima (visible λ max ) than the substrate malachite green [12].…”