Malachite Green Decolorization Research Articles

New bacterial strains isolated from Tunisian biotopes: A sustainable enzymatic approach for decolorization and detoxification of Congo Red and Malachite Green.

Seven bacterial strains, isolated from various Tunisian biotopes, were investigated for Congo Red (CR) and Malachite Green (MG) decolorization. The isolated strains underwent morphological and biochemical tests, including assessments for antibiotic sensitivity as well as biofilm formation. One selected strain, ST11, was partially identified as Paenibacillus sp. strain ST11. The newly isolated crude bacterial filtrates (NICBFs) effectively decolorized CR and MG. Specifically, six and seven NICBFs were found to be effective for degrading CR (150mgl-1) and MG (50mgl-1), respectively. Under non-optimized conditions, CR and MG could be decolorized up to 80% within 6-12h. The degradation products of CR and MG, characterized by UV-visible and FT-IR techniques, demonstrated both decolorization and transformation, highlighting the role of enzymes in dye degradation. Phytotoxicity and cytotoxicity studies evaluated the impact of treated and untreated CR and MG. Some NICBFs showed promise as powerful biological tools, reducing and sometimes detoxifying CR and MG, commonly used as fertilizers. The potential applications of these NICBFs in decolorization and bioremediation of dye-rich textile effluents were explored. The screening also identified environmentally friendly, cost-effective bacterial strains adaptable to various conditions through phytotoxicity and cytotoxicity studies.

Enhanced catalytic performance and pH stability of Streptomyces Laccase Y230R and its degradation of malachite green

The escalating threat of malachite green (MG) pollution poses significant risks to ecosystems. Saturation mutation targeting Tyr230 of small laccase (SLAC) from Streptomyces coelicolor yielded Y230R, exhibiting a remarkable 104 % increase in specific activity. Notably, this mutation achieved dual enhancements in both activity and pH stability. Molecular dynamics simulation revealed higher structural stability of Y230R compared to wild-type (WT) across varying pH levels. The increased count of hydrogen bonds in Y230R compared to WT may be contribute to its stability. Y230R demonstrated superior catalytic efficiency (67.0 %) in MG decolorization, maintaining over 90 % activity after 30 min incubation in MG solution (500 mg/L), highlighting enhanced tolerance compared to WT. Molecular docking analysis attributed the differential catalytic effects on MG and ABTS to structural disparities and hydrogen bonding. Y230R stands as a promising composite mutant for future laccase engineering and industrial applications.

Utilizing banana peel in conjunction with TiO2 photocatalyst for the efficient decolorization of malachite green

Porous materials are frequently integrated into TiO2 photocatalysts due to their enhanced surface area and reaction efficiency. This study aimed to enhance the efficiency of wastewater treatment by developing a TiO2 combined with banana peel (BP) through the sol-gel method. The TiO2/BP composite was extensively analyzed using a range of methods, such as X-ray diffraction (XRD), field emission transmission electron microscopy (FESEM), energy dispersive X-ray (EDX) analysis, diffuse reflectance spectroscopy (DRS UV–vis), photoluminescence spectra (PL), and Brunauer–Emmett–Teller (BET) analysis. Subsequent evaluation of the photoactivity of the TiO2/BP composite compared to bare TiO2 particles revealed a noteworthy enhancement in decolorizing malachite green (MG) dye under visible light. Furthermore, recyclability testing further demonstrated consistent performance for up to four cycles, highlighting the potential application of this porous material-based photocatalytic composite in wastewater treatment.

Harnessing the potential of a novel lignin-degrading Streptomyces sp. MS-S2 from wood-feeding termite for malachite green decolorization and detoxification

Lignin and synthetic dyes share complex structural similarities and relevant management difficulties, which should be effectively addressed towards environmental sustainability. Under this scope, the quest for oxidative enzyme-producing microorganisms with a view to efficiently valorizing organic pollutants is of utmost importance. The intestinal bacteria of wood-feeding termites represent a unique source of valuable enzymes. The decolorization efficiency of five different dyes, including malachite green (MG), methyl violet, anihiline blue, reactive red, and reactive blue, after 12 h of degradation by the MS-S2 bacterial strain was recorded to be 98.2, 17.5, 8.7, 4.6, and 3.28%, respectively. Several physico-chemical parameters were then optimized to accelerate MG degradation, including pH, temperature, glucose, and yeast extract concentration. Streptomyces sp. strain MS-S2 completely decolorized MG (50 mg/L) within 2 h under optimized conditions when the cultivation medium was amended with 5 g/L glucose and 0.08 g/L yeast extract at pH 8 and incubated at 28 °C. After MG degradation, the enzyme activities of manganese peroxidase (4.605 U/L) and laccase (45.185 U/L) were estimated. To comprehend the degradation process of MG by the MS-S2 strain, UV-Vis spectroscopy, Fourier transform infrared (FTIR), and gas chromatography-mass spectrometry (GC-MS) analyses were carried out to ascertain the possible degradation mechanism. The metabolites identified, such as 2,6-Bis (tert-butyl) phenol and [4-(dimethylamino) phenyl] phenyl, suggest that MG was broken down into less toxic compounds for further degradation. MS-S2 exhibited outstanding characteristics that could make it suitable for the bioremediation of MG dye in an industrial setting.

Engineering Site 228 of Streptomyces coelicolor Laccase for Optimizing Catalytic Activity.

Malachite green (MG) poses a formidable threat to ecosystems and human health. Laccase emerges as a promising candidate for MG degradation, prompting an investigation into the catalytic activity modulation of a small laccase (SLAC) from Streptomyces coelicolor, with a focus on amino acid position 228. Through saturation mutagenesis, five mutants with a 50% increase in the specific activity were generated. Characterization revealed notable properties, Km of E228F was 8.8% of the wild type (WT), and E288T exhibited a 133% kcat compared to WT. Structural analyses indicated improved hydrophobicity and electrostatic potential on the mutants' surfaces, with the stable E228F-ABTS complex exhibiting reduced flexibility, possibly contributing to the observed decrease in turnover rate. Mutants demonstrated enhanced MG decolorization, particularly E228G. Site 228 acts as a crucial functional control switch, suggesting its potential role in SLAC engineering. This study provides insights into laccase modulation and offers promising avenues for enzymatic bioremediation applications.

Zeolitic imidazolate framework biocomposite as a visible light-assisted photocatalyst: Synthesis (in-situ and blending), regeneration, and decolorization of Malachite Green

To overcome the limitations of current water treatment technologies, it is essential to develop non-toxic materials with high removal capabilities. Herein, novel green biocomposite beads, CS/ZIF-8/TiO2 (CZT), based on chitosan modified with zeolitic imidazolate framework (ZIF-8) and titania (TiO2) was introduced. The interesting and noteworthy features of this new biocomposite are its green synthesis, biocompatibility, and easy separation ability. The composite beads effectively decolorize Malachite Green (MG) dye solution using visible LED light. In the present study, the efficiency of three components of CZT biocomposite, which were synthesized by two different methods (in situ and blending), was compared to investigate the effect of the synthesis method, as well as the synthesis with two different amounts of TiO2 (0.2 g, and 0.4 g) to investigate the effect of TiO2. The prepared materials through the XRD, SEM, EDS, FTIR, DRS, TGA, and RAMAN analyses were characterized. The synergistic effect of ZIF-8, TiO2, and chitosan in the biocomposite increased the photo-decolorization ability of the MG dye under visible-light irradiation. The decolorization at the optimum pH (pH = 6.5) after 180 min reached 94.5% and at the natural pH (pH = 3.93) after 300 min reached 98.2%. The photocatalytic decolorization reaction of the biocomposite followed zero-order kinetics.

Shewanella chilikensis MG22 isolated from tannery site for malachite green decolorization in microbial fuel cell: a proposed solution for recirculating aquaculture system (RAS)

Malachite Green (MG) dye of the triphenylmethane group is a toxic compound used in the aquaculture industry as an antifungal agent, however, it can accumulate in fish and pose toxicity. The present work aims to remove MG in Microbial Fuel Cell (MFC) as a sustainable and eco-friendly solution. Out of six samples, the highest malachite green degradation was obtained by a sample obtained from Robiki tannery site in agar plates in 24 h at 37 °C. Robiki sample was used to inoculate the anodic chamber in Microbial Fuel cell, the resulting average electricity production was 195.76 mV for two weeks. The decolorization average was almost 88%. The predominant bacteria responsible for MG decolorization and electricity production were identified using 16S rRNA as Shewanella chilikensis strain MG22 (Accession no. OP795826) and formed a heavy biofilm on the anode. At the end of the decolorization process, MG was added again for re-use of water. The results showed efficiency for re-use 3 times. To ensure the sterility of treated water for re-use, both UV and filter sterilization were used, the latter proved more efficient. The obtained results are promising, MFC can be used as recirculating aquaculture system (RAS). The same aquaculture water can be treated multiple times which provides a sustainable solution for water conservation.Graphical

Silver-platinum bimetallic nanoparticles as heterogeneous persulfate activator for the oxidation of malachite green

Fabrication of noble metal nanoparticles by using green chemical method with plant extract as reducing agent to the in situ oxidation toxic water contaminants have been the subject of various investigators due to their enhanced catalytic efficiencies. This paper describes the extraction of caffeic acid from Artemisia herba-alba aqueous extract, and preparation of silver (Ag), platinum (Pt), and silver-platinum (Ag-Pt) nanoparticles with caffeic acid as a reducing and capping agent. The as-prepared Ag-Pt NPs was used as a heterogeneous activator of persulphate (K2S2O8) for the in situ chemical oxidation of malachite green (MG). The Ag-Pt NPs shows no surface Plasmon resonance absorption band. The malachite green dye was completely decolorized in presence of Ag-Pt/K2S2O8 system. SO4-• and HO• radicals generated by the cleavage of S2O82- peroxide activation with Ag-Pt were responsible for the MG decolorization as well as mineralization. The Ag-Pt NPs acted as a sacrificial electron donor. The Ag-Pt NPs were characterized by using conventional techniques such as, UV–visible, FTIR, SEM, TEM, EDX, XPS, and XRD spectroscopic methods.

Evaluation of two colorimetric microplate microtiter tests for susceptibility testing of clinical isolates of Mycobacterium tuberculosis to first-line antituberculosis drugs.

Drug-resistance tuberculosis (TB) is one of the most important global public health problems. Accurate and rapid drug-susceptibility testing is critical for the effective treatment of TB patients. Various colorimetric methods are used for anti-TB drug-susceptibility testing (DST) and minimum inhibitory concentration (MIC) determination. This study was conducted to evaluate the resazurin microtiter assay (REMA) and malachite green decolorization assay (MGDA). A total of 65 Mycobacterium tuberculosis strains isolated from patients with suspected TB using REMA and malachite green microtiter assay methods were tested against streptomycin (SM), isoniazid (INH), rifampicin (RIF), and ethambutol (ETB). The Mycobacterial Growth Indicator Tube 960 DST method was accepted as the gold standard in the evaluation of test results. The sensitivity of REMA and MGDA tests was found to be 87.5% and 62.5% for INH, respectively. RIF and SM sensitivity for both tests was 100%. While ETB sensitivity was 81.8 for the REMA test, this rate was 60% for the MGDA test. Specificity of both tests varied between 92.5% and 98.2% according to the drug types. REMA and MGDA are a simple, rapid, and low cost. They can be used as an alternative test for drug-susceptibility testing and MIC determination. Extensive studies and standardization are needed for the routine use of both tests.

Optimization of the Fabrication of Sustainable Ceramsite Adsorbent from Coal Fly Ash/Waterworks Sludge/Waste Glass for Decolorization of Malachite Green

As a traditional dye, malachite green (MG) poses a threat to our environment and health. To decolorize MG, a composite ceramsite adsorbent composed of coal fly ash (CFA), sewage treatment sludge (STS), and waste glass (WG) with a quality ratio of 3 : 3 : 4, respectively, was prepared. The optimal preparation parameters were determined as follows: preheating [Formula: see text], sintering [Formula: see text], and sintering [Formula: see text]. Under optimal conditions, scanning electron microscopy (SEM) images show that the X-Com-ceramsite sample exhibits rough features and a porous structure. The obtained X-Com-ceramsite has a good MG decolorization effect (92% decolorization rate with an initial MG concentration of 56.876 mg/L). The [Formula: see text] value of MG can reach up to 37.6 mg/g. The retention degree of MG in the X-Com-ceramsite with a relatively higher pH is stronger, and the adsorption process is spontaneous and endothermic. Synchronous fluorescence, two-dimensional correlation spectroscopy (2D-COS), and Fourier transform infrared spectroscopy (FT-IR) proved that the sensitivity of the C-O/C-O-O functional groups of the carbohydrates on the surface of the X-Com-ceramsite has a higher binding affinity toward MG as the initial concentration of MG changes.

Modelling the Decolorization of Malachite Green by Staphylococcus aureus

Dyes plays an important role in our everyday life. From manufacturing plastics, paints, textile and even pills contain traces of dye used. With the ever-increasing demand for dye with growing world populations, the use of synthetic dyes has grown linearly. Bioremediation of dyes using microorganisms is on the rise. The ability to accurately predict the rate of bioremediation relies upon the gathering of the accurate rate of decolourisation, which is often inaccurately obtained by natural logarithm transformation of the decolourisation process over time. In this instance, a nonlinear regression of the curve needs to be carried out utilising available rate models. Hence, various primary models such as modified Logistic, modified Gompertz, modified logistics, modified Richards, modified Schnute, Baranyi-Roberts, Buchanan-3-phase, von Bertalanffy and the Huang models were utilized to fit the specific decolourisation rate. Several models failed to converge and was omitted and only Huang, Baranyi-Roberts, modified Gompertz, modified Richards and modified Logistics were able to model the data while other models failed to converge and were omitted. The best model based on statistical analysis was Baranyi Roberts with the highest value for Adjusted Coefficient of Determination and the lowest values for RMSE, AICc, HQC and BIC and the closest value to 1.0 for accuracy and bias factors. The Baranyi-Roberts fitted curve was found to conform to normality tests and is adequate to be used to fit the experimental data. The parameters obtained from this exercise can be utilized for further secondary modelling exercise to gleam information on how substrate (dye) affect the rate of decolourisation of the substrate.

Mathematical Modeling of the Inhibition Kinetics of Malachite Green Decolorization by Staphylococcus aureus

Basic Green 4 or Malachite Green (MG) is an important dye that found great usage in controlling fish pathogens. The use of MG has been banned but developing, and third-world countries still found applications for this dye. Bioremediation of dyes using microorganisms is on the rise. The ability to accurately predict the rate of bioremediation relies upon the gathering of the accurate rate of decolourisation, which is often inhibited at high concentrations of the toxicant. Various secondary models such as Monod, Haldane, Teissier, Aiba, Yano and Koga, Hans-Levenspiel, Webb and the Luong models were utilized to fit the specific decolourisation rate, and most of them show visually acceptable fitting except Monod and Teissier. The best model based on statistical analysis was Hans-Levenspiel with the highest value for the adjusted coefficient of determination and the lowest values for RMSE, AICc, HQC and BIC and the closest value to 1.0 for accuracy and bias factors. The Hans-Levenspiel model was found to conform to normality tests and is adequate to be used to fit the experimental data. The normality tests carried out using tests such as the Kolmogorov-Smirnov, Wilks-Shapiro and the D'Agostino-Pearson omnibus K2 test shows that the model pass the normality tests with p >0.05 for all normality tests carried out. The experimental data obtained indicates that Malachite Green is toxic and slows down the rate of decolourisation at higher concentrations. The maximum MG specific biodegradation rate (qmax), half-saturation concentration (KS), maximum allowable MG concentration (Sm), and the shape factors (n and m) were 0.136 h-1, 0.56 mg/L, 2691 mg/L, -33.31 and 35.12, respectively. The parameters obtained from this exercise can be utilized to model the bioremediation of MG in the future.

Microbial Degradation, Spectral analysis and Toxicological Assessment of Malachite Green Dye by Streptomyces exfoliatus.

Malachite green (MG) dye is a common environmental pollutant that threatens human health and the integrity of the Earth’s ecosystem. The aim of this study was to investigate the potential biodegradation of MG dye by actinomycetes species isolated from planted soil near an industrial water effluent in Cairo, Egypt. The Streptomyces isolate St 45 was selected according to its high efficiency for laccase production. It was identified as S. exfoliatus based on phenotype and 16S rRNA molecular analysis and was deposited in the NCBI GenBank with the gene accession number OL720220. Its growth kinetics were studied during an incubation time of 144 h, during which the growth rate was 0.4232 (µ/h), the duplication time (td) was 1.64 d, and multiplication rate (MR) was 0.61 h, with an MG decolorization value of 96% after 120 h of incubation at 25 °C. Eleven physical and nutritional factors (mannitol, frying oil waste, MgSO4, NH4NO3, NH4Cl, dye concentration, pH, agitation, temperature, inoculum size, and incubation time) were screened for significance in the biodegradation of MG by S. exfoliatus using PBD. Out of the eleven factors screened in PBD, five (dye concentration, frying oil waste, MgSO4, inoculum size, and pH) were shown to be significant in the decolorization process. Central composite design (CCD) was applied to optimize the biodegradation of MG. Maximum decolorization was attained using the following optimal conditions: food oil waste, 7.5 mL/L; MgSO4, 0.35 g/L; dye concentration, 0.04 g/L; pH, 4.0; and inoculum size, 12.5%. The products from the degradation of MG by S. exfoliatus were characterized using high-performance liquid chromatography (HPLC) and gas chromatography-mass spectrometry (GC-MS). The results revealed the presence of several compounds, including leuco-malachite green, di(tert-butyl)(2-phenylethoxy) silane, 1,3-benzenedicarboxylic acid, bis(2-ethylhexyl) ester, 1,4-benzenedicarboxylic acid, bis(2-ethylhexyl) ester, 1,2-benzenedicarboxylic acid, di-n-octyl phthalate, and 1,2-benzenedicarboxylic acid, dioctyl ester. Moreover, the phytotoxicity, microbial toxicity, and cytotoxicity tests confirmed that the byproducts of MG degradation were not toxic to plants, microbes, or human cells. The results of this work implicate S. exfoliatus as a novel strain for MG biodegradation in different environments.

Synthesis and Photocatalytic Activity of Ruthenium-Titania for Enhanced Decolorization of Malachite Green under Visible Light Illumination

The photodecolorization of malachite green (MG) dye was effectively done using Ruthenium-doped TiO2 photocatalysts under visible light illumination. X-ray diffraction analysis revealed that anatase and rutile peaks were both found in undoped TiO2 while only anatase peaks were present in Ru-doped TiO2 systems which were calcined at 500°C. The 0.008 Ru-TiO2 photocatalysts calcined at 300°C showed broader peaks compared to those calcined at 500°C. Further increase of calcination temperature to 700°C promotes the transformation of anatase to rutile peaks. The photocatalytic activity of TiO2 was found to increase with the addition of Ruthenium ions, from 20% for undoped TiO2 to 87% for 0.80 Ru-doped TiO2. The maximum photocatalytic removal of MG dye was achieved using 1.50 g∙L-1 of catalyst loading for 0.008 Ru-doped TiO2. The TiO2 photocatalysts prepared at a calcination temperature of 500°C showed higher photodecolorization efficiency compared to those calcined at 300°C and 700°C. Kinetic studies revealed that the photodecolorization of MG using Ru-doped TiO2 followed a first order kinetics.

Decolorization of malachite green in aqueous solution via MgO nanopowder

Water is one of the essential primary resources for life and development on the planet, where many industrial activities depend on it, but some industries lead to water pollution. Hence, we need economical and effective ways to address the contamination. This article describes the production and utilization of MgO nanopowder using thermal decomposition as an economical and efficient method for malachite green decolorization. The MgO nanopowder was analyzed via various techniques for morphology, cryptography, surface area, etc. Batch adsorption tests have been performed as a function of contact time, pH, and initial dye concentration to study their impact on decolorization of malachite green via MgO nanopowder. The result verified the target nanopowder's production with crystallite size 20.16 nm and a relative surface area of 19.84 m2 /g. MgO nanopowder was employed to decolorize malachite green dye in an aquatic solution utilizing a batch method. The findings revealed that the maximum adsorption capacity value was 232.26 mg/g. The adsorption was found to follow the Freundlich isotherm models and follow the pseudo-second-order kinetics

Bioremediation Potential of Chlorella vulgaris and Nostoc paludosum on azo Dyes with Analysis of Metabolite Changes

Microalgae have been used widely in bioremediation processes to degrade or adsorb toxic dyes. Here, we evaluated the decolorization efficiency of Chlorella vulgaris and Nostoc paludosum against two toxic dyes, crystal violet (CV) and malachite green (MG). Furthermore, the effect of CV and MG dyes on the metabolic profiling of the studied algae has been investigated. The data showed that C. vulgaris was most efficient in decolorization of CV and MG: the highest percentage of decolorization was 93.55% in case of MG, while CV decolorization percentage was 62.98%. N. paludosum decolorized MG dye by 77.6%, and the decolorization percentage of CV was 35.1%. Metabolic profiling of C. vulgaris and N. paludosum were performed using NMR spectroscopy. Based on 1D and 2D NMR data, 43 compounds were identified in the polar extract of C. vulgaris, while 34 polar metabolites were successfully determined in N. paludosum. The identified compounds included carbohydrates, amino acids, organic acids, dipeptides, steroids and phenols. Statistical analysis was carried out to recognize the pattern of metabolite variation between control and dye treated samples. Principal component analysis (PCA) and hierarchical cluster analysis showed that samples treated with MG are clearly separated from the control in both types of algae. Based on heat map data, the level of carbohydrates and amino acids concentrations are strongly affected by bioremediation of MG dye compared with CV dye. In conclusion, the present study proved that CV and MG dyes are considered as stress factors and the studied algae species exert their bioremediation activity without the dyes being absorbed into the cells.

Decolorization of Malachite green dye by Stenotrophomonas maltophilia a compost bacterium

BackgroundThe release of triphenylmethane dyes, like malachite green (MG) and crystal violet (CV), into the environment is a cause of concern due to its toxicity, mutagenicity and carcinogenicity.ResultA bacterial strain that is capable of decolorizing both dyes was isolated from the composted neem oil-seed cake. The strain was characterized as Stenotrophomonas maltophilia based on the 16S rRNA gene sequence and designated as isolate TPMD-1. The kinetic study of the dye degradation revealed the efficiency of the above isolate to degrade MG. The effect of substrate concentration, pH, temperature, and agitation on the decolorization of MG by the isolate was also studied. The MG degradation rate was slightly more in neutral pH at 28–30 °C and 150 rpm. The UV-spectroscopy, HPLC, and FTIR analyses of the dye sample before and after bacterial treatment revealed the high ability of S. maltophilia TPDM-1 in the removal of MG from the media. The genetic snapshot of the isolate by PCR amplification and sequencing showed the presence of genes 'lac’ and ‘tmr’ that codes for laccase and triphenylmethane reductase.ConclusionThis study presented the first report of Stenotrophomonas maltophilia in the degradation and detoxification of MG dye by oxidoreduction, which could be used for the bioremediation of aquatic environments contaminated by MG.

Coculture of white rot fungi enhance laccase activity and its dye decolorization capacity

Fungal cocultures can promote complex interactions that result in physiological and biochemical alterations that favor the synergic and more efficient action of extracellular enzymes such as laccase. Thus, coculture can be used as a strategy to increase enzymatic activity, dye degradation, and bioremediation of textile effluents. This study aimed to evaluate the coculture effect of Lentinus crinitus, Pleurotus ostreatus, Pycnoporus sanguineus, and Trametes polyzona on laccase activity, mycelial biomass production, and in vitro decolorization of azo, anthraquinone, and triphenylmethane dyes. The species were cultivated in liquid medium in monoculture and coculture in paired combinations for 15 days to determine the laccase activity and produced mycelial biomass. The enzymatic extracts of fungal cultivations were used in decolorization tests of reactive blue 220 (RB220), malachite green (MG), and remazol brilliant blue R (RBBR). Pleurotus-Trametes, Lentinus-Pleurotus, and Lentinus-Trametes cocultures increase laccase activity compared to respective monocultures. Lentinus-Pycnoporus, Lentinus-Trametes, Lentinus-Pleurotus, and Pleurotus-Trametes cocultures stimulate mycelial biomass production in relation to their respective monocultures. The enzymatic extracts of monocultures and cocultures promoted the decolorization of all dyes. RB220 dye presented fast decolorization. In 24 h, all extracts reached maximum decolorization and the greatest color reduction percentage was 90% for Pleurotus-Trametes coculture extract. Pleurotus-Trametes extract also increased the decolorization of MG and RBBR dyes when compared to their respective monocultures in 48 h and 72 h, respectively. However, RBBR dye presented the greatest resistance to decolorization.

A highly thermotolerant laccase produced by Cerrena unicolor strain CGMCC 5.1011 for complete and stable malachite green decolorization

Laccases are a class of multi-copper oxidases with important industrial values. A thermotolerant laccase produced by a basidiomycete fungal strain Cerrena unicolor CGMCC 5.1011 was studied. With glycerin and peptone as the carbon and nitrogen sources, respectively, a maximal laccase activity of 121.7 U/mL was attained after cultivation in the shaking flask for 15 days. Transcriptomics analysis revealed an expressed laccase gene family of 12 members in C. unicolor strain CGMCC 5.1011, and the gene and cDNA sequences were cloned. A glycosylated laccase was purified from the fermentation broth of Cerrena unicolor CGMCC 5.1011 and corresponded to Lac2 based on MALDI-TOF MS/MS identification. Lac2 was stable at pH 5.0 and above, and was resistant to organic solvents. Lac2 displayed remarkable thermostability, with half-life time of 1.67 h at 70 ºC. Consistently, Lac2 was able to completely decolorize malachite green (MG) at high temperatures, whereas Lac7 from Cerrena sp. HYB07 resulted in accumulation of colored MG transformation intermediates. Molecular dynamics simulation of Lac2 was conducted, and possible mechanisms underlying Lac2 thermostability were discussed. The robustness of C. unicolor CGMCC 5.1011 laccase would not only be useful for industrial applications, but also provide a template for future work to develop thermostable laccases.

Optimization of environmental parameters by Plackett-Burman design and response surface methodology for the adsorption of Malachite green onto Gracilaria edulis

Gracilaria edulis, marine red seaweed was harvested from the coastal area of South Tamil Nadu, Rameswaram and was evaluated for the adsorption of Malachite Green. The algal biomass which is used as the adsorbent was pretreated for the activation of the binding sites on its surface. The environmental factors for the degradation process involve the pH (4–8), Biomass concentration (1 to 5 g/L), Dye concentration (10 to 20%), Time (120–180 min), Temperature (30–40 °C), and agitation-static were evaluated using Minitab 18 software. For the optimization process, the statistical techniques Plackett–Burman Design (PBD) and Response Surface Methodology (RSM) approaches were used. Plackett-Burman Design was performed for Malachite Green (MG) gave twelve trials and resulted in three significant parameters such as pH, temperature, and dye concentration. RSM was further used to determine the optimum parameters for the degradation. The maximum decolorization of Malachite Green was attained at pH = 4.5, dye concentration = 17, Temperature = 37 °C.