Increasing Chromium Content Research Articles

Synthesis of double carbide (Ti,Cr)C with a different Cr content produced by electro thermal explosion

In this paper we report the preparation of double carbide (Ti,Cr)C with a chromium content of 10 ÷ 30 at% by electrothermal explosive synthesis (ETE). This method allows synthesis to be carried out at high temperature with minimal holding time. The ETE method is favourable for the formation of dense carbide ceramics. The synthesized samples were characterized by X-ray diffraction and scanning electron microscopy. It was found experimentally that the unit cell parameter of the double carbide decreases linearly with increasing chromium content. The DFT calculations also confirmed the dependence of the unit cell parameter (Ti,Cr)C on the chromium content according to Vegard's law and show changes in the cell shape and distance between Cr–Cr layers with increasing chromium content. The pDOS diagram shows that an increase in chromium content leads to an excess of d∗ electrons on the π∗ orbitals, which has a destabilizing effect on the double carbide structure.Crystal Orbital Hamiltonian (COHP) analysis of the electronic structure of the double carbide, partitioning the energy of the band structure into bonding, non-bonding and anti-bonding energy regions, showed the influence of chromium content on its stability.

Development of the passive film during passivation in passivating electrolytes containing sodium molybdate

The impact of sodium molybdate on passive films formed on lean duplex stainless steel (STS 329 FLD) was investigated. Elemental depth distribution was examined using glow discharge optical emission spectroscopy, while the analysis covered passive film capacitance, molybdenum's chemical state, and corrosion resistance. The addition of sodium molybdate to the passivation electrolyte resulted in a reduction of iron content in the iron-rich layer (from 48 % to 38 %), an increase in chromium content in the enhanced chromium layer (from 33 % to 42 %), and the presence of molybdenum on the film surface. Electrical impedance spectroscopy measurements indicated a significant increase in the capacitance of the passive film. Furthermore, molybdenum was identified as molybdate. Electrochemical anodic polarization curves revealed that the corrosion potential rose with the addition of sodium molybdate to the nitric acid electrolyte. This improvement in corrosion resistance was attributed to molybdate adsorption on the outermost part of the passive film, preventing chloride adsorption or penetration. Additionally, the corrosion current density decreased due to the presence of the chromium-rich layer.

PREDICTION OF ELECTROCHEMICAL PROCESSES OF LOCAL DISSOLUTION OF STAINLESS STEELS. PART 2. ANALYTICAL AND SIMULATION MODELING OF PROCESS DYNAMICS

To analyze the process of pitting corrosion, a state graph was used, which displays the possible states of local dissolution of chromium-nickel steels, taking into account the additional state "unstable passivation of macropitting". The developed analytical model for calculating the process before the formation of stable pitting is based on homogeneous Markov chains. The calculation of conditional probabilities of system changes from one possible state to another determines the time in the VisualStudio 2010 environment on the platform of NetFramework using the C# programming language. A comparison of the calculation of states with “unstable passivation of macropitting” (UPM) and without it allowed us to establish for stainless steels (12X18N10T, 10X17N13M2T, 08X22N6T) that the formation time of stable pitting taking into account UPM is less than the formation time without it, but more for 08X22N6T steel, which is due to the increased chromium content in its composition. A simulation model (SM) has been created, which is based on the Monte Carlo method, in which a random number generator is used to implement random processes of local dissolution due to SM, a sequence of states in which the system is located before its transition to a stable state is obtained. Also, due to this model, it became possible to consider the change in the potential of the system in the process of local dissolution of the studied steels. The use of two modeling approaches taking into account the state of the UPM allowed us to establish that IT is better consistent with experimental results both on a quantitative and qualitative level. An algorithm for selecting the values of the mode parameters is proposed, which became the basis for predicting the formation of macropitting processes. For citation: Vinogradova S.S. Prediction of electrochemical processes of local dissolution of stainless steels Part 2. Analytical and simulation modeling of process dynamics. ChemChemTech [Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol.]. 2024. V. 67. N 6. P. 119-126. DOI: 10.6060/ivkkt.20246706.6972.

Focusing on the corrosion resistance enhancement of HRB400 rebar by Cr addition in the marine environment

The corrosion resistance of Cr reinforced HRB400 rebar in the marine environment was investigated. The addition of Cr increases the amount of Cr(OH)3 and α-FeOOH in the passivate film, resulting in a denser passivate film structure. This enhanced passivation film inhibits localized corrosion. The pitting potential and critical chloride concentration (CTL) of the steel increased with the increase in chromium content, indicating improved corrosion resistance of the steel. On the other hand, an increase in the concentration of Cl- in solution leads to a decrease in the pitting potential and resistance of the steel, which reduces the corrosion resistance. At higher Cl- concentrations, the Cl- ions form an electrochemical interface with the steel surface, resulting in a sharp decrease in the Rf value. In addition, the gradual decrease in solution pH leads to a decrease in the pitting potential and CTL of HRB400 and 1.5Cr steel. The corrosion resistance was also found to be reduced, pH reduction accelerated the intrusion of chloride ions, which led to a severe breakdown of the passivation film.

Performance and properties evolution of near-term accident tolerant fuel: Cr-doped UO2

Chromium-doped UO2 fuel has received significant interest due to the ability for chromium to produce pellets with large average grain size (>30 μm), which has shown to increase fission gas retention during operation. Sintering of chromium-doped UO2 pellets was pursued with oxygen potential and sintering atmosphere controlled to tailor the final microstructure of the material. Chromium additions in this study ranged from 750 to 7800 ppm. Cr concentrations were studied pre and post sintering using Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES). Effects of chromium content on lattice parameter and microstructure were examined with X-ray diffraction (XRD) and scanning electron microscopy (SEM). Contraction of the UO2 lattice parameter was observed, as well as enlargement of grain size with increasing chromium content up to 4900 ppm Cr2O3. SEM indicated Cr incorporation within the matrix and the formation of chromium oxide precipitates throughout the microstructure at high Cr concentrations. Evaluation of thermophysical properties of Cr-doped UO2 pellets were conducted up to 1200 °C to illustrate their evolution with increased dopant concentration and microstructural changes. The results show that grain size is maximized at 52 μm with Cr2O3 concentration equal to 4900 ppm; however, grain size decreases at higher Cr2O3 concentrations. No significant changes were observed in specific heat capacity, linear thermal expansion, and coefficient of thermal expansion compared to undoped UO2. The thermal conductivity also decreased through the incorporation of Cr2O3 dopants above 750 ppm and is shown to be ∼15 % lower than reported UO2 values.

Composition-dependent brittleness and ductility of the multicomponent phase (Fe, Cr)23(C, B)6 in Fe–Cr–B–C alloys: First-principles calculations and modeling

(Fe, Cr)23(C, B)6, as a strengthening phase in Fe–Cr–B–C alloys, has not been reported on the relationship between its properties and composition over the entire composition range. (Fe, Cr)23(C, B)6 tends to exhibit brittleness, which is difficult to regulate through traditional experiments. The mechanical properties of (Fe, Cr)23(C, B)6 phase in Fe–Cr–B–C alloy have been studied by first principles calculation. With the help of CALPHAD method, the distribution of elastic constant, modulus, hardness and fracture toughness in the whole component space was obtained, so that the suitable component with good wear resistance and strong toughness was obtained. The mechanical properties of (Fe, Cr)23(C, B)6 phase is better in the range of ∼0.4–0.6 at. % B and ∼0.5–0.7 at. % Cr. The mechanism of these differences is explained in terms of state density, bond length, population analysis and differential charge density, as the addition of boron and the increase in chromium content led to a significant increase in the formation of covalent bonds between metals and non-metals, in which these bonds play a decisive role. The combination of the first principles calculation and the CALPHAD model provides a feasible model for constructing the composition-property relationship of medium entropy compounds.

Investigation of High-Temperature Oxidation of Homogeneous and Gradient Ni-Cr-Al Coatings Obtained by Detonation Spraying

The high-temperature oxidation of homogeneous and gradient coatings based on Ni-Cr-Al obtained by detonation spraying is investigated. To assess the resistance to high-temperature oxidation of Ni-Cr-Al coatings, cyclic tests were carried out at a temperature of 1000 °C for 50 cycles. The assessment of high-temperature oxidizing ability was carried out by measuring the weight gain of samples after each cycle. After high-temperature oxidation tests, the morphology and chemical composition of the coating structure in the cross-section were investigated using SEM/EDS. The phase composition of the samples was studied by X-ray diffraction (XRD) phase analysis. Visual analysis of the sample surface under study after high-temperature oxidation showed that the surface of homogeneous or gradient Ni-Cr-Al coatings remained undamaged. The results of X-ray phase analysis showed the peaks of Al2O3 in Ni-Cr-Al gradient coatings are more expressed and intense compared to homogeneous coatings of Ni-Cr-Al. Gradient coatings also retain an increased chromium content compared to homogeneous Ni-Cr-Al coatings. This increased chromium content can slow down mixing or diffusion between different phases of the material at their boundary, which, in turn, contributes to increasing the resistance of the gradient coating to oxidation.

Dielectric, reflection loss and physicochemical studies of Cr doped Ba–Sr based W type hexagonal ferrites for microwave absorption applications

The utilization of hexagonal structures in nano ferrites has been employed for absorption because of their dielectric, attenuation characteristics, and reflection losses. Electromagnetic pollution is one of the significant issues in cleaning the environment. Electronic devices produce pollution and are hazardous to human health. Therefore, ferrite materials have been used for absorption purposes. In this study, the impact of chromium substitution on the structural and dielectric specifications of the Barium-strontium-based W-type hexagonal ferrites has been investigated and used for microwave absorption application. The sol-gel auto-ignition process prepared w-type hexagonal ferrites with Ba0.5Sr0.5Mg2CrxFe16-xO27 (x = 0.0, 0.1, 0.2, 0.3, and 0.4). According to XRD examination, the formation of single-phase W-type hexagonal ferrites was proven. The synthesized composition is confirmed to be nanocrystalline because the calculated crystallite size value is in the nanometer range. FTIR analysis confirmed the structure of W-type hexagonal ferrite. Raman spectroscopic study examined the vibrational and rotational modes of molecules. Survey spectra of XPS, which include Ba, Sr, Mg, Fe, Cr, and O, confirmed the presence of all constituent elements. SEM analysis confirmed that the sample contains grains with a hexagonal platelet shape. The results showed that increasing chromium concentration reduced the dielectric permittivity, tan loss, and ac conductivity. At x = 0.4, the reflection loss value is very low. The recorded value is −79.62 dB, corresponding to a frequency of 5.92 GHz, with a thickness of 1.75 mm. Because of this, W-type hexagonal ferrites are suitable for a wide range of electronic applications, including microwave absorbers, high-density recording media, and multilayer chip inductors. These applications have made it possible to functionalize these materials in order to enhance device performance and lower the size, weight, and cost of devices while also fostering the development of new technologies that have significantly improved the quality of our daily lives.

Synthesis and Characterization of Cr-Doped Pb2Fe2O5 Thin Films by Reactive Magnetron Sputtering

Multiferroic materials, which exhibit simultaneous ferroelectricity, ferromagnetism, and ferro-elasticity, have attracted significant attention due to their multifunctional properties. Coupling between ferroelectric and magnetic properties has led to the development of non-volatile memory devices, transducers, magnetic field sensors, and other applications. Pb2Fe2O5 (PFO) is a promising multiferroic material due to it simultaneously exhibiting ferroelectricity and ferromagnetism at room temperature. Doping with aliovalent ions, such as Cr3+, has been proposed as an effective method for enhancing the ferroelectric and magnetic properties, consequently leading to the enhancement of multiferroic properties. The investigation shows that the lead ferrite phase (220) was present in all samples, but its abundance reduced with increasing synthesis temperature due to lead desorption. Dielectric measurements revealed that PFO films with highest Cr concentration had the highest polarization (Pr) of 72.2 μC cm−2. The study also found that the magnetization of PFO films was up to 9.5·10−7 μAm2 at an ambient temperature of 5 K, and the magnetic ordering temperature was 363 K, corresponding to the magnetic ordering temperature of chromium oxides. The morphology of Cr doped PFO films changed with increasing chromium content, resulting in a reduction in grain size and an increase in the film density.

Revival of rhombohedral structure and complex magnetic response in (La,Cr) codoped BiFeO3

The polycrystalline ceramics of Bi0.83La0.17Fe1-xCrxO3 (BLFCO) have been synthesized by the solid-state reaction method to investigate the features of structural phase coexistence and complex magnetic response. The coexistence of the R3c rhombohedral and Pbam orthorhombic structures has been revealed by X-ray diffraction and Rietveld refinement. Selected-area Raman scattering spectra are used to further confirm a mixed phase state as both phonon vibrations of these phases are detectable. An unusual revival of the R3c phase is observed with increasing chromium concentration. The compound displays an intriguing weak magnetic response and some unique phenomena, such as the magnetic aging and field step-dependent hysteresis loop. The electric-field-controlled magnetism shows a complex behavior due to the interplay of the phase boundary ferromagnetism and structural phase transition.

Hexavalent Chromium Inhibited Zebrafish Embryo Development by Altering Apoptosis- and Antioxidant-Related Genes.

This study aimed to assess the effects of hexavalent chromium on zebrafish (Danio rerio) embryo development. The zebrafish embryos were treated with solutions containing chromium at different concentrations (0.1, 1, 3.125, 6.25, 12.5, 50, and 100 µg/mL). The development of zebrafish embryos was estimated by the determination of survival rate, heart rate, and the measurement of larvae body length. Real time RT-PCR and Western blot were performed to assess the expression of apoptosis- and antioxidant-related genes. The results showed that the reduced survival rate of zebrafish embryos and larvae was associated with an increase in chromium concentration. The exposure of higher concentrations resulted in a decrease in body length of zebrafish larvae. In addition, a marked increase in heart rate was observed in the zebrafish larvae under chromium treatment, especially at high concentrations. The real-time RT-PCR analysis showed that the transcript expressions for cell-cycle-related genes (cdk4 and cdk6) and antioxidant-related genes (sod1 and sod2) were downregulated in the zebrafish embryos treated with chromium. Western blot analysis revealed the upregulation of Caspase 3 and Bax, while a downregulation was observed in Bcl2. These results indicated that hexavalent chromium induced changes in zebrafish embryo development by altering apoptosis- and antioxidant-related genes.

Effect of Different Levels of Chromium With and Without Organic Sources on the Availability of Primary Nutrients and Yield of Wheat

A pot experiment (2020-21) was conducted with different levels of -1 chromium (0, 10,20,30,40,50 mg kg ) with and without FYM or vermicompost (25g/10 kg soil) in completely factorial redomised block design in net house of the Department of Soil Science & Agricultural Chemistry, Institute of Agricultural Sciences, Banaras Hindu University, Varanasi. The experiment was conducted in factorial completely randomized design (FCRD). Maximum plant height was recorded in Cr0+VC (21.6 cm) followed by Cr0+FYM (19.8 cm)at 30 DAS. The increasing chromium concentration decrease the chlorophyll content in all the treatments Highest grain and straw yields of wheat were associated with Cr0+VC treatment, highest available N, P, K was recorded with Cr20+VC, Cr30+VC and Cr10+VC respectively.

Heat Treatment of High-Performance Ferritic (HiperFer) Steels.

High-performance Ferritic (HiperFer) steels are a novel class of heat-resistant, fully ferritic, Laves phase precipitation hardened materials. In comparison to conventional creep strength-enhanced 9-12 wt.% Cr ferritic-martensitic steels, HiperFer features increased mechanical strength, based on a thermodynamically stable distribution of small (Fe,Cr,Si)2(Nb,W) Laves phase precipitates, and-owing to its increased chromium content of 17 wt.%-improved resistance to steam oxidation, resulting in superior temperature capability up to 650 °C. Previous publications focused on alloying, thermomechanical processing, and basic mechanical property evaluation. The current paper concentrates on the effect of heat treatment on microstructural features, especially Laves phase population, and the resulting creep performance. At 650 °C and a creep stress of 100 MPa, an increase in rupture time of about 100% was achieved in comparison to the solely thermomechanically processed state.

Experimental Research on the Wear Behavior of Materials Used in the Manufacture of Components for Cement Concrete Mixers

Mixers used in the production of cement concrete operate under special conditions such as mechanical stresses, abrasive-erosive friction phenomena, and corrosive working environments. In this paper, the authors aimed to establish a correlation between the chemical composition of mixer blade materials and their wear behavior. Three types of alloyed (chromium) cast iron were used for an experimental program that included three sets of tests in accelerated wear conditions which replicated the actual working environment (mixture of mineral aggregate, sand, cement, and water). The tribological tests were carried out using a Baroid tribometer. The results indicated that regardless of the test environment, cast iron with the highest chromium content exhibited the best wear resistance. However, it cannot be concluded that the wear resistance of the studied cast iron materials increases as a direct result of an increase in chromium content. For a chromium content of less than 25%, a better tribological behavior was observed for cast iron with a lower chromium content (of about 4%) than for cast irons with a higher chromium content (of about 9%).

Synthesis and Properties of Octet NiCr Alloy Lattices Obtained by the Pack Cementation Process

NiCr alloys with different components were obtained by pack chromation and homogenization heat treatment of octet Ni lattice. The microstructure, alloy composition, microhardness and quasi-static compression properties of the NiCr lattice were tested. The results showed that after homogenization heat treatment, the NiCr alloy lattice had an austenitic structure with uniform composition. Compared with the pure nickel lattice, the microhardness, compressive strength, elastic modulus and energy absorption of the NiCr lattice increased with the increase of chromium content. The microhardness, specific strength, specific modulus and specific energy absorption of the Ni-45Cr alloy were 363 HV, 11.1 MP/(g/cm3), 1169.1 MP/(g/cm3) and 10 J/g, respectively, which were attributed to the solid solution strengthening provided by chromium and the increase in density. NiCr alloy lattices have high strength and toughness and may have potential applications in high-temperature filters or heat exchangers.

An Experimental Investigation on Welding of 5Cr- 0.5Mo Material for Heat Exchanger Application

Chromium-Molybdenum (Cr-Mo) steels are widely used in oil refineries, petrochemical industries and power plants forvarious applications, including heat exchangers, pressure vessels and piping. The main advantage of these steels are theimproved creep strength due to addition of Molybdenum and enhanced corrosion resistance imparted by chromium.5Cr-0.5Mo steels are extensively used in seamless tubing in petroleum industry because of their corrosion resistanceagainst oils and crude containing hydrogen sulphides and other corrosive agents. The main advantage of 5Cr-0.5Mo steelsis the improved oxidation resistance because of increased Chromium content. In modern refineries, a more recent andcommon application of this steel grade is in the fabrication of desulphurization plants used for the production of cleanlow Sulphur petrol and diesel fuels.In recent past, L&T heavy engineering received a challenging project for manufacturing of 2 nos.of high-pressure exchangersinvolving 5Cr-0.5Mo material having a wall thickness of 85 mm. The severe operating conditions also demanded a stainlesssteel347 weld overlay on inner surface of the vessel. Producing crack-free weldments in 5Cr-0.5Mo which are adequate fora given service would conventionally entail correct choice of filler metal, stringent welding conditions including preheat,proper welding technique and post-weld heat treatment (PWHT). This paper describes about development of weldingprocedures for this material and our experience in successful fabrication of high pressure exchangers with 5Cr-0.5Mo asthe material of construction.

Stoichiometry driven tuning of physical properties in epitaxial Fe3-xCrxO4 thin films

Tuning magnetic and electronic transport properties in spinel oxides requires a faithful description between chemical composition and cation site-occupation. Here this challenge is addressed using Fe3-xCrxO4 thin films grown by oxygen-assisted molecular-beam epitaxy within a wide range of composition (0.0 ≤ x ≤ 1.2). Spectroscopic measurements (e.g., X-ray magnetic circular dichroism), refined by theoretical simulations (e.g., crystal field multiplet), are performed to establish a quantitative link between chromium content, Fe2+/Fe3+ site-occupation and macroscopic physical properties of the layers. It is found that Fe3-xCrxO4 thin films (i) delay the transition from inverse to normal spinel configuration with increasing chromium content and (ii) promote collinear spin structure, at odds with bulk material. As a result, strong antiferromagnetic interactions are preserved between spins in tetrahedral and octahedral spinel sublattices, so that chromium-rich thin films exhibit Curie temperatures above room temperature and higher magnetization. Electron hopping is also favored by this singular cation distribution and electronic band gap is smaller than expected for these thin films. The cation site-occupation is therefore a key feature to consider for applications of Fe3-xCrxO4 thin films in spintronics and photocatalysis, as it enables manipulation of magnetic properties (Curie temperature and magnetization) and band gap engineering.

Изменение состава и коррозионно-электрохимических свойств хромоникелевой стали 03Х18Н11 при имплантации ионов аргона, кислорода и азота

The effect of implantation of argon, oxygen and nitrogen ions on the physicochemical structure of the surface and the corrosion-electrochemical behavior of chromium-nickel steel 03Cr18Ni11has been studied. Methods of electrochemical polarization (EP), atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS) were used. Ion implantation of argon, oxygen and nitrogen leads to an increase in the corrosion resistance of steel 03Cr18Ni11 both in a neutral environment and in the presence of a corrosion activator (chloride anions), while irradiation with argon ions is most effective. It was found that after implantation of argon ions, a partial etching of the steel surface occurs, i.e. an increase in the true surface. This, in turn, facilitates the onset of the passive state. At the same time, the use of oxygen and nitrogen ions leads to smoothing of the surface. AFM data indicate that the studied steel treated with argon ions exhibits the greatest resistance to local corrosion. The implantation of oxygen and argon ions reduces the overall corrosion to the greatest extent. It is important to note that deep craters and traces of pitting corrosion do not form on the surface of the steel. The XPS data show that after ion implantation, there was a change in the concentration of the elements that make up the steel in the near-surface layers of the material in the depth of the implanted layer compared with the non-irradiated sample. It is established that the surface layers of steel are enriched with chromium atoms during ion implantation. This process occurs most intensively when samples are treated with argon ions. In this case, mixed chromium and iron oxides are formed, contributing to the passivation of the steel surface. Also, the process of ion implantation is accompanied by oxidation of the surface of the steel under study. This is confirmed by an increase in the oxygen content in the surface layers. To the greatest extent, this process occurs during implantation of oxygen ions. After corrosion tests, an increased chromium content is also observed on the surface of steel treated with Ar+ ions, which confirms the formation in this case of strong chromium oxides that remain on the surface during the corrosion of steel. The analysis of the fine structure of the XPS spectra showed that under the action of argon ions, the oxygen of surface oxides is redistributed in favor of chromium atoms and the formation of strong mixed iron and chromium oxides of the spinel type, including Fe2+, Fe3+, Cr3+ and Cr6+ compounds. It is important to note that although chromium oxides are also formed during oxygen implantation and in the same quantities as during argon implantation, the protective properties of the resulting compounds are noticeably lower. Therefore, not only the chemical composition is important, but also the structure of the resulting layers. It can be assumed that the high kinetic energy of heavy argon ions affects both the formation of a developed surface relief and the formation of strong mixed iron and chromium oxides of the spinel type.

Trace Element Contents in Maize following the Application of Organic Materials to Reduce the Potential Adverse Effects of Nitrogen.

The plants cultivated in loamy sand contained less iron, manganese, copper, cobalt, nickel, and zinc while containing more chromium, lead, and cadmium than in sand. This study was launched to use organic materials in the form of humic acids (HA) to reduce the potential negative effects of excessive nitrogen fertiliser (ammonium nitrate, urea, and urea and ammonium nitrate solution-UAN) application rates (160 mg N kg-1 soil) on the trace element contents in maize in two soils differing in granulometric composition. HA were applied into the soil three times during the maize vegetation: before the sowing, at the five-leaf unfolded stage, and at the intensive shoot growth stage. The HA doses amounted to 0, 0.05, 0.10, and 0.15 g kg-1 soil. Urea fertilisation increased the cadmium, lead, chromium, and nickel contents and reduced the iron content in maize on both soils. UAN contributed to an increased chromium content being higher than that caused by urea and to reduced iron content in the aboveground parts of maize, as compared to the objects with ammonium nitrate. In the series with ammonium nitrate, the highest dose of HA reduced the manganese, zinc, iron, and cobalt contents in maize on both soils. In the series with urea, however, their reducing effect on the copper and iron contents in maize on both soils was noted. The study also demonstrated a positive reduction in the contents of many other trace elements in maize under the influence of the application of HA (particularly, their highest dose). However, it only concerned one of the soils under study. The application of HA into the soil can be effective in reducing the trace element content in plants and can mitigate the adverse environmental impact of intensive agricultural production.

Whole-genome sequencing of biofilm-forming and chromium-resistant mangrove fungus Aspergillus niger BSC-1

Filamentous fungus Aspergillus niger has gained significant industrial and ecological value due to its great potential in enzymatic activities. The present study reports the complete genome sequence of A. niger BSC-1 which was isolated from Indian Sundarban mangrove ecosystem. The study revealed that the genome of A. niger BSC-1 was 35.1 Mbp assembled in 40 scaffolds with 49.2% GC content. A total of 10,709 genes were reported out of which 10,535 genes were predicted for encoding the proteins. BUSCO assessment showed 98.6% of genome completeness indicating high quality genome sequencing. The genome sequencing of A. niger BSC-1 revealed the presence of rodA and exgA genes for initial adhesion to surface and Ags genes for matrix formation, during biofilm growth. OrthoVenn2 analysis revealed that A.niger BSC-1 shared 9552 gene clusters with the reference strain A. niger CBS554.65. Semi-quantitative RT-PCR analysis unveiled the role of Ags1 and P-type ATPase in fungal biofilm formation and chromium (Cr) resistance, respectively. During biofilm growth the expression of Ags1 significantly (P < 0.0001; two-way ANOVA followed by Sidak's multiple comparisons test) increased with respect to planktonic culture revealing the possible involvement of Ags1 in biofilm matrix formation. Expression of P-type ATPase gene was significantly upregulated (P < 0.0001; one-way ANOVA followed by Dunnett's multiple comparisons test) with the increasing chromium concentration in the fungal culture. Besides, several other genes encoding metalloprotease, copper and zinc binding proteins, and NADH-dependent oxidoreductase were also found in the genome of A. niger BSC-1. These proteins are also involved in heavy metal tolerance and nanofabrication indicating that this filamentous fungus A. niger BSC-1 could be potentially utilized for chromium detoxification through biofilm or nanobiremediation.