Efficient malachite green biodegradation by Pseudomonas plecoglossicide MG2: process optimization, application in bioreactors, and degradation pathway

Abstract

Microbial degradation of synthetic dyes is considered a promising green dye detoxification, cost-effective and eco-friendly approach. A detailed study on the decolorization and degradation of malachite green dye (MG) using a newly isolated Pseudomonas plecoglossicide MG2 was carried out. Optimization of MG biodegradation by the tested organism was investigated by using a UV–Vis spectrophotometer and the resultant degraded products were analyzed by liquid chromatography–mass spectrometry and FTIR. Also, the cytotoxicity of MG degraded products was studied on a human normal retina cell line. The optimum conditions for the significant maximum decolorization of MG dye (90–93%) by the tested organism were pH 6–7, inoculum size 4–6%, and incubation temperature 30–35 °C, under static and aerobic conditions. The performance of Pseudomonas plecoglossicide MG2 grown culture in the bioreactors using simulated wastewater was assessed. MG degradation (99% at 100 and 150 mg MG/l at an optimal pH) and COD removal (95.95%) by using Pseudomonas plecoglossicide MG2 culture were the best in the tested culture bioreactor in comparison with that in activated sludge or tested culture-activated sludge bioreactors.The FTIR spectrum of the biodegraded MG displayed significant spectral changes, especially in the fingerprint region 1500–500 as well as disappearance of some peaks and appearance of new peaks. Twelve degradation intermediates were identified by LC–MS. They were desmalachite green, didesmalachite green, tetradesmalachite green, 4-(diphenylmethyl)aniline, malachite green carbinol, bis[4-(dimethylamino)phenyl]methanone, [4-(dimethylamino)phenyl][4-(methyl-amino)phenyl]methanone, bis[4-(methylamino)phenyl]methanone, (4-amino- phenyl)[4-(methylamino)phenyl]methanone, bis(4-amino phenyl)methanone, (4-amino phenyl)methanone, and 4-(dimathylamino)benzaldehyde. According to LC–MS and FTIR data, two pathways for MG degradation by using Pseudomonas plecoglossicide MG2 were proposed. MG showed cytotoxicity to human normal retina cell line with LC50 of 28.9 µg/ml and LC90 at 79.7 µg/ml. On the other hand, MG bio-degraded products showed no toxicity to the tested cell line. Finally, this study proved that Pseudomonas plecoglossicide MG2 could be used as an efficient, renewable, eco-friendly, sustainable and cost-effective biotechnology tool for the treatment of dye wastewater effluent.

Production and optimization of surfactin produced from locally isolated Bacillus halotolerans grown on agro-industrial wastes and its antimicrobial efficiency

“…The inoculated culture plates were incubated at 37 o C for 48 h and the separated bacterial colonies were picked up and preserved using nutrient agar slants at 4 o C for further studies. The mixed colonies were also subjected to further purification under the serial dilution method [ 12 ].…”

Pyracantha coccinea biochar synthesis, characterization, and use in the removal of cationic dyes

“…The need to create sophisticated treatment methods to eliminate MB and MG from wastewater has been emphasized by several recent studies such as biodegradation [14], photodegradation [15], advanced oxidation processes, adsorption [16][17], phytoremediation [18], photocatalytic decomposition [19][20], activated carbon [21][22] and electrochemical destruction [23][24], are currently used to remove MG. However, these processes are expensive and are unable to effectively treat the variety of wastewater that contains dyes.…”