Pathway and Molecular Mechanisms for Malachite Green Biodegradation in Exiguobacterium sp. MG2

Abstract

Malachite green (MG), N-methylated diaminotriphenylmethane, is one of the most common dyes in textile industry and has also been used as an effective antifungal agent. However, due to its negative impact on the environment and carcinogenic effects to mammalian cells, there is a significant interest in developing microbial agents to degrade this type of recalcitrant molecules. Here, an Exiguobacterium sp. MG2 was isolated from a river in Yunnan Province of China as one of the best malachite green degraders. This strain had a high decolorization capability even at the concentration of 2500 mg/l and maintained its stable activity within the pH range from 5.0 to 9.0. High-pressure liquid chromatography, liquid chromatography-mass spectrometry and gas chromatography–mass spectrometry were employed to detect the catabolic pathway of MG. Six intermediate products were identified and a potential biodegradation pathway was proposed. This pathway involves a series of reactions of N-demethylation, reduction, benzene ring-removal, and oxidation, which eventually converted N-methylated diaminotriphenylmethane into N, N-dimethylaniline that is the key precursor to MG. Furthermore, our molecular biology experiments suggested that both triphenylmethane reductase gene tmr and cytochrome P450 participated in MG degradation, consistent with their roles in the proposed pathway. Collectively, our investigation is the first report on a biodegradation pathway of triphenylmethane dye MG in bacteria.

Malachite green decolorization by the filamentous fungus Myrothecium roridum – Mechanistic study and process optimization

“…An obvious inhibitory effect of metyrapone was also observed on MG decolorization by Mycobacterium chelonae, M. avium and Exiguobacterium sp. MG2 (Jones and Falkinham, 2003;Wang et al, 2012).…”

“…In recent years, many studies have focused on various microorganisms capable of MG removal, including bacteria, yeast, filamentous fungi and algae (Du et al, 2011;Karimi et al, 2012;Lv et al, 2013;Shedbalkar and Jadhav, 2011;Wang et al, 2012;Yan et al, 2014). The use of microbe-based methods in MG decomposition http://dx.doi.org/10.1016/j.biortech.2015.07.008 0960-8524/Ó 2015 Elsevier Ltd. All rights reserved.…”

“…The most frequently mentioned factors involved in MG decolorization are the activities of cytochrome P-450, triphenylmethane reductase and extracellular lignin-modifying enzymes, particularly laccases (Fu et al, 2013;Gao et al, 2015;Jasiń ska et al, 2015). The literature data also indicate that dye decolorization may be mediated by nonenzymatic low-molecular-weight compounds that are resistant to high temperatures, which are also described as thermostable low-molecular-weight factors (LMWF) (Gomaa et al, 2008;Gomaa, 2012;Wang et al, 2012).…”

Nanocrystalline ZnO doped lanthanide oxide: An efficient photocatalyst for the degradation of malachite green dye under visible light irradiation

“…As there is a continuous generation of OH radicals in the Photocatalytic Dye Degradation by ZnO doped Lanthanide oxide under Visible Light Irradiation reaction system, attack of OH radicals occurs spontaneously on the organic moiety [23]. On further reaction, the byproducts may undergo continuous degradation due to OH radical attack to bring about a benzene ring removal [24] and ring opening to completely mineralize the material to yield carbon dioxide and water as the end by-products [25]. A schematic representation is shown in Fig.…”

Combination of photoreactor and packed bed bioreactor for the removal of ethyl violet from wastewater

“…was found in malachite-green-containing wastewater in extremely high concentrations (Wang et al, 2012). D. immobilis was isolated from concentrated triphenylmethane wastewater (Liu et al, 2013).…”