Decolorization of recalcitrant dyes by a multicopper oxidase produced by Iodidimonas sp. Q-1 with iodide as a novel inorganic natural redox mediator

Accelerated biodecolorization and detoxification of synthetic textile dye Acid Maroon V by bacterial consortium under redox mediator system

The treatment of textile industrial wastewater is an important concern owing to its negative impact on the biosphere. The present study highlighted dye decolorization potential of bacterial consortium EDPA containing Enterobacter dissolvens AGYP1 and Pseudomonas aeruginosa AGYP2 in the presence of redox mediators. Rapid decolorization of Acid Maroon V (100 mg l-1) was achieved in the presence of lawsone compared to other redox mediators. The dye decolorization was best fitted with first order kinetics with higher reaction kinetics (k1 = 0.328 h-1) and regression coefficient (R2 = 0.979). The removal of dye by the consortium was 1.47 times faster in 8 h with 0.01 mM lawsone. The consortium EDPA was able to decolorize 1200 mg l-1 concentration of dye with apparent R max , K m and R max /K m values 1000 mg l-1 h-1, 5000 mg l-1 and 0.2 h-1, respectively. The lawsone-mediated system could decolorize the dye 80.44% in 10 h at the end of 11 dye spiking cycle. The superior biodecolorization of 14 different textile dyes was obtained in the presence of lawsone-mediated system. The intracellular enzyme activities of azoreductase, NADH-DCIP reductase, laccase, manganese peroxidase and lignin peroxidase increased significantly. The sequential microaerophilic-aerobic incubation resulted into 89.31% reduction of total aromatic amines. The microbial toxicity, phytotoxicity and genotoxicity measurements revealed biotransformation of toxic nature of dye Acid Maroon V into non-toxic metabolites by the action of consortium EDPA, and thus its suitability for biotreatment of dye containing industrial effluents.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13205-023-03466-6.

The Genus Iodidimonas: From Its Discovery to Potential Applications

The genus Iodidimonas was recently proposed in the class Alphaproteobacteria. Iodidimonas strains are aerobic, mesophilic, neutrophilic, moderately halophilic, and chemo-organotrophic. They were first discovered in natural gas brine water containing a very high level of iodide (I−). They exhibited a unique phenotypic feature of iodide oxidation to form molecular iodine (I2). Iodidimonas was also enriched and isolated from surface seawater supplemented with iodide, and it is clearer now that their common habitats are those enriched with iodide. In such environments, Iodidimonas species seem to attack microbial competitors with the toxic form I2 to occupy their ecological niche. The iodide-oxidizing enzyme (IOX) purified from the Iodidimonas sp. strain Q-1 exhibited high catalytic efficiency for iodide and consisted of at least two proteins IoxA and IoxC. IoxA is a putative multicopper oxidase with four conserved copper-binding regions but is phylogenetically distinct from other bacterial multicopper oxidases. The IOX/iodide system could be used as a novel enzyme-based antimicrobial system which can efficiently kill Bacillus spores. Furthermore, the IOX/iodide system can be applied to the decolorization of recalcitrant dyes, where iodide may function as a novel inorganic natural redox mediator.

Decolorization of cationic dyes under alkaline conditions by Iodidimonas sp. Q-1 multicopper oxidase

Previously, we found that a multicopper oxidase (IOX) produced by Iodidimonas sp. Q-1, an iodide (I^-)-oxidizing marine bacterium, exhibited significant decolorization activity toward various anionic dyes. In this study, the potential capacity of IOX for decolorization of cationic dyes such as malachite green (MG), crystal violet (CV), and methylene blue (MB) was determined. Decolorization of the dyes by IOX exhibited significant pH dependence, and effective decolorization was observed under alkaline conditions. At an optimum pH of 9.5, IOX decolorized more than 90% of MG, CV, and MB within 30 min, 2 h, and 6 h, respectively. The addition of iodide was indispensable for decolorization, suggesting that this halide ion serves as a redox mediator. Decolorization products of MG showed less toxicity than MG against Escherichia coli cells. These results suggest that this IOX-iodide system can be used for the decolorization and detoxification of cationic dyes under alkaline conditions.

Decolourisation of textile dye by laccase: Process evaluation and assessment of its degradation bioproducts

Biodegradation of environmentally hazardous synthetic dyes by enzymes has been achieved the highest interest in recent years. In this work, we optimized Remazol Brilliant Blue R (RBBR) dye biodegradation by Arthrographis kalrae derived laccase via the Box-Behnken design (BBD) approach of the surface response methodology (RSM). Optimization of dye decolourisation by one variable at a time (OVAT) approach resulted in optimal dye decolourisation at laccase dose (2 IU mL^-1), pH (7.0), temperature (35 °C), incubation time (240 min), and initial dye concentration (100 mg L^-1). The optimized process through BBD enhanced dye decolourisation (97.18%). Fourier Transform Infrared Spectroscopy and UV-Visible Spectrophotometry have proven biodegradation. In addition, in comparison to untreated samples, the laccase-treated dye sample showed relatively less phyto- and cytotoxic effect on Allium cepa L. Extra Precision Glide docking exhibited the binding affinity score of -5.355 kcal mol^-1, between laccase-RBBR complex.

Using textile industrial sludge, sewage wastewater, and sewage sludge as inoculum to degrade recalcitrant textile dyes in a co-composting process: an assessment of biodegradation efficiency and compost phytotoxicity

Recalcitrant dyes found in textile wastewater represent a threat for sustainable textile production due to their resistance to conventional treatments. This study assessed an alternative co-composting system for the treatment of recalcitrant textile dyes where textile industrial sludge, sewage wastewater, or sewage sludge were used as microbial compost inocula. The biodegradation efficiency of bioreactor trials and compost quality of the co-composting system were assessed by visible spectrophotometry and by a phytotoxicity test. The co-composting system (dry weight (dw) basis) consisted of 200 g of restaurant organic residues + 200 g sewage sludge (or 100 mL sewage wastewater, or 200 g textile sludge) + 100 mL of a 10% dye solution (Reactive Red 195, or Synolon Brown, or Orange Remazol, or Yellow Synozol, or Reactive Orange 122, or Reactive Black 5). After 60 days of composting, all dyes were biodegraded according to spectrophotometric data, with efficiency varying from 97.2 to 99.9%. Inoculum efficiency ranking was textile sludge > sewage sludge > sewage wastewater. Regarding compost quality, a phytotoxicity study with lettuce showed no toxicity effect. Thus, co-composting can be a low-cost and efficient method for recalcitrant textile dye biodegradation and for managing textile sludge in terms of waste recycling, contributing to environmental sustainability.

Sustainable Denim Bleaching by a Novel Thermostable Bacterial Laccase

Laccases have emerged as environment-friendly multifaceted biocatalysts for diverse biotechnological applications. Here, we isolated a high molecular weight (88 kDa) extremophilic laccase (LacT) from Brevibacillus agri, with the aim to exploit its extreme characters in denim bleaching. LacT has been characterized as a thermostable, acidophilic enzyme with high salt, organic solvent, and divalent metal tolerance properties. Denim bleaching efficiency of LacT was optimum at pH 4.0 and appeared to be surpassing over other reported laccases. LacT also exhibited remarkable efficacy in the decolorization of water-soluble health hazardous azo-dyes, and thus transpired to be a promising bio-bleaching and dye decolorizing agent.

Ecofriendly biodegradation of Reactive Black 5 by newly isolated Sterigmatomyces halophilus SSA1575, valued for textile azo dye wastewater processing and detoxification

A total of seven yeast strains from 18 xylanolytic and/or xylose-fermenting yeast species isolated from the wood-feeding termite Reticulitermes chinenesis could efficiently decolorize various azo dyes under high-salt conditions. Of these strains, a novel and unique azo-degrading and halotolerant yeast, Sterigmatomyces halophilus SSA1575, has been investigated in this study. This strain could significantly decolorize four combinations of a mixture of dyes. It showed a high capability for decolorizing Reactive Black 5 (RB5) even at 1,500 mg L⁻¹. The strain SSA1575 still showed a high capability for decolorizing a 50 mg L⁻¹ RB5 with a salt mixing at a NaCl concentration of up to 80 g L⁻¹. It also exhibited significant ability to decolorize repeated additions of dye aliquots, with a reduction in time of up to 18 h. Most of the tested carbon and nitrogen sources could significantly enhance a RB5 decolorization. However, this process was inhibited by the addition of sucrose and sodium nitrate. NADH-dichlorophenol indophenol (NADH-DCIP) reductase and lignin peroxidase were determined as the key reductase and oxidase of S. halophilus SSA1575. Finally, strain SSA1575, can effectively detoxify RB5 into non-toxic products. Overall, S. halophilus SSA1575, might be a promising halotolerant yeast valued for the treatment of various textile effluents with high salinity.