Bioremediation Of Chromium Research Articles

Bioremediation of hexavalent chromium using Beauveria bassiana SSR5: adsorption mechanisms, kinetics, and characterization

Hexavalent chromium (Cr(VI)) poses a significant ecological threat due to environmental pollution. The urgent need for an economically viable solution to remove Cr(VI) and restore ecological balance is evident. This study explores the adsorption isotherms of Cr(VI) uptake by newly isolated B. bassiana SSR5 dead fungal biomass. The batch uptake experiments, conducted under controlled pH and temperature conditions, reveal that dead fungal biomass from B. bassiana has an outstanding ability to adsorb Cr(VI). The optimal adsorption occurs at pH levels of 1 and ≤1.5, achieving a maximum capacity of 113.2 mg per gram of dry weight at an initial concentration of 300 mg/L. The adsorption capacity is strongly influenced by the solution pH, with peak values noted at pH 1.0. Conversely, temperature variations show minimal impact on the uptake capacity. All adsorption isotherms exhibit a strong correlation with the standard Langmuir equation, indicating a monolayer adsorption mechanism. The kinetic profile illustrates a rapid uptake process, achieving equilibrium within 30 min, suggesting the involvement of chemisorption. The process primarily involves ion exchange and electrostatic interactions between positively charged sites on the fungal biomass and negatively charged Cr(VI) ions at lower pH levels, facilitating the reduction of Cr(VI) to Cr(III) and enhancing adsorption. This study underscores the potential of B. bassiana dead fungal biomass as an effective biosorbent for Cr(VI) removal from wastewater and tannery effluent. The intriguing mechanism and the pH effect on the conversion of Cr(VI) to Cr(III) ions by the fungal cell wall warrant further exploration.

Modern-Day Green Strategies for the Removal of Chromium from Wastewater.

Chromium is an essential element in various industrial processes, including stainless steel production, electroplating, metal finishing, leather tanning, photography, and textile manufacturing. However, it is also a well-documented contaminant of aquatic systems and agricultural land, posing significant economic and health challenges. The hexavalent form of chromium [Cr(VI)] is particularly toxic and carcinogenic, linked to severe health issues such as cancer, kidney disorders, liver failure, and environmental biomagnification. Due to the high risks associated with chromium contamination in potable water, researchers have focused on developing effective removal strategies. Among these strategies, biosorption has emerged as a promising, cost-effective, and energy-efficient method for eliminating toxic metals, especially chromium. This process utilizes agricultural waste, plants, algae, bacteria, fungi, and other biomass as adsorbents, demonstrating substantial potential for the remediation of heavy metals from contaminated environments at minimal cost. This review paper provides a comprehensive analysis of various strategies, materials, and mechanisms involved in the bioremediation of chromium, along with their commercial viability. It also highlights the advantages of biosorption over traditional chemical and physical methods, offering a thorough understanding of its applications and effectiveness.

“Efficient novel fungal-enriched biochar formulation for hexavalent chromium bioremediation”

Chromium (Cr), a key element in industrial processes such as leather tanning, poses severe environmental hazards, particularly its hexavalent form, Cr(VI), which is highly toxic and prevalent in tannery effluents/sludge. The persistence and toxicity of Cr(VI) necessitate the development of effective remediation strategies to mitigate its environmental impact. This study investigated the potential of Trichoderma yunnanense (NBRICRF_97) and its combination with 0.5% sugarcane bagasse biochar (SBC) for the reduction of Cr(VI). The results demonstrated that T. yunnanense alone achieved a 91.04% reduction of 50 mg L−1 Cr(VI) within 72 h. Combined with 0.5% SBC, the reduction efficiency increased to 99.65% within 48 h. However, the efficiency decreased at higher concentrations (200 mg L−1). The combination also improved fungal growth and increased extracellular ChrR enzyme activity (13.07 U mg−1 protein compared to the control). Total glutathione activity was boosted by 161.07% at 100 mg L−1 Cr(VI). Antioxidant enzymes (SOD, POD, CAT) and proline mitigated oxidative stress and FTIR analysis revealed changes in fungal cell wall functional groups (-OH and -NH) upon Cr(VI) exposure. SEM-EDX confirmed chromium deposition on fungal surfaces. These results underscore the Cr(VI) detoxification capabilities of T. yunnanense and the synergistic benefits of SBC, suggesting a promising bioremediation strategy for Cr(VI)-contaminated environments. The integration of T. yunnanense with SBC offers a sustainable and cost-effective approach for the bioremediation of Cr(VI)-contaminated sites, with potential for implementation in large-scale environmental cleanup efforts.

Bioremediation of chromium(VI) and arsenic(III) using isolated microalgal (Chlorella thermophilia): Analysis of growth, biomolecular compositions (carbohydrate, protein, chlorophyll) and biosorption kinetics

Microalgae are under research focus for the production of bio-fuels by bioremediation of different kinds of wastewater like industry and municipality and other sources. The current study deals with investigations towards the capability of isolated microalgae (Chlorella thermophilia) for the removal of Cr(VI) and As(III) by re-modeling their extracellular and intracellular compositions. This isolated microalgae was able to grow in the presence of Cr(VI) up to 1 mg L−1 concentration and As(III) up to 15 mg L−1 concentration. Carbohydrate content in microalgae increased to 28 % in 0.4 mg L−1 of Cr(VI) and 46 % in 10 mg L−1 of As(III) respectively as compared to control. The protein content of Chlorella thermophilia grown in Cr(VI) [1 mg L−1] and As(III) [15 mg L−1] containing media decreased by almost 61 % and 9 % respectively as compared to control. Growth kinetics results revealed the decline in biomass to 10 % and 15 % under exposure of Cr(VI) [0.6 mg L−1] and As(III) [10 mg L−1] respectively compared to control. Chlorella thermophilia showed the removal of As(III) within the range of 70–91 % [at an As(III) concentration of 0.5–10 mg L−1], while removal of Cr(VI) was within 50–65 % [at a Cr(VI) concentration of 0.2–0.6 mg L−1]. Interestingly, almost 60 % of Cr(VI) was removed within 6 days of microalgae growth while removal of As(III) was slow and steadily increased to 80 % in 30 days. Our results showed the prospects of Chlorella thermophilia as a sustainable resource for the removal of heavy metals [Cr(VI) and As(III)] from wastewater. In addition, the enrichment of carbohydrates in microalgae during their growth would be supportive for the production of biofuels.

Identification of Bacteria Capable of Chromium Bioremediation from the Environment

With the increased urbanization and industrial development, the environment is getting polluted severely day by day. In Bangladesh, the capital city Dhaka is surrounded by a circular river system, most of which are highly polluted due to discharge of municipal and industrial untreated waste water that has been overloaded with different types of toxic heavy metals. Cr (VI) being used in various activities of industries and its improper treatment lead to contamination of the environment. This study aimed to isolate bacteria with chromium bioremediation potential from the environment. A total of 71 bacteria were isolated, of which all grew in the presence of 100 ppm, 93% in 200 ppm, 46% in 400 ppm, 6% in 600 and 4% in 1000 ppm chromium. Fourteen bacteria selected for chromium reduction by Diphenyl Carbazide Assay showed 23-89% reduction. Of these 14 isolates, 5 were tested for biosorption of chromium. Variable sorption of upto 69% was observed. The 16s rDNA of 6 candidate bacteria were sequenced. These isolates were identified as Kurthia gibsonii, Acinetobacter schindleri, Pseudomonas aeruginosa, Exigubacterium sp., Rhodococcus sp., and Bacillus sp. The reduction potential was found to be highest for Bacillus species (78%) and lowest for Kurthia gibsonii (4.8%). This study has successfully identified six potential bacterial candidates for the bioremediation of chromium (VI). Further research into the mechanisms adopted by these bacteria and genetic manipulation will help to formulate a single or mixture of isolates that can efficiently remove hexavalent chromium from polluted water. Plant Tissue Cult. & Biotech. 34(1): 71-81, 2024 (June)

Bacterial Bisorption as an Approach for the Bioremediation of Chromium Contaminated Soils: An Overview

Study’s Novelty/Excerpt This study presents comprehensive overview of the roles of various bacterial genera, including Alcaligens, Achromobacter, and Bacillus, in the biosorption of chromium from contaminated soils, highlighting specific factors influencing biosorption efficiency. It uniquely addresses the optimization of environmental conditions such as pH, temperature, and nutrient availability to enhance large-scale biosorption processes, bridging gaps noted in previous literature regarding the scalability of bacterial biosorption. Additionally, the manuscript underscores the necessity for further research in biotechnology and molecular engineering to fully harness the potential of bacterial biosorption for chromium remediation, presenting a forward-looking perspective on advancing this bioremediation strategy. Full Abstract Chromium possesses detrimental effects on the health of both plants and animals. Biosorption is a process where biological materials (bacteria, fungi, algae, or agricultural waste) are used to remove pollutants from contaminated sites. Conventional methods of remediating heavy metal-contaminated soils, such as excavation and chemical treatment, are expensive and disruptive, making them less desirable. Factors influencing bacterial biosorption efficiency are promising approaches involving bacteria to remove heavy metals such as Chromium, lead, nickel, cadmium, arsenic, etc., from contaminated soil. Some bacterial genera involved in biosorption include Alcaligens, Achromobacter, Acinetobacter, Alteromonas, Arthrobacter, Burkholderia, Bacillus, Enterobacter, Flavobacterium, and Pseudomonas. These bacteria can adsorb heavy metals such as Chromium and biotransform them into less toxic forms. Some factors influencing bacteria biosorption efficiency include pH, temperature, concentration, bacterial surface compositions, metal ion characteristics, and soil composition. Challenges associated with using bacteria for biosorption, as outlined in previous literature, include the slowness of the process and the fact that it may not be suitable for large-scale application, even though many other authors have proven its applicability on a large scale. Also, the key quality needed from the bacterial biosorbent must be tolerating the heavy metals. Another area of focus in current research is optimizing environmental conditions, such as temperature, pH, and nutrient availability, to achieve a more efficient biosorption at a larger scale. This overview highlighted the roles of bacteria in the biosorption of chromium heavy metal as a strategy for the bioremediation of Chromium contaminated soil. Conclusively, bacterial biosorption has a great potential for use in Chromium- contaminated soil remediation, and more research is needed to fully realize this potential, especially in biotechnology and molecular engineering.

STRATEGIES OF TOXIC CHROMIUM (VI) MITIGATION FROM TANNERY EFFLUENTS: A REVIEW

Hexavalent chromium i.e., Cr (VI) is highly toxic and carcinogenic it enters the environment through several anthropogenic activities. It is spuriously used in various industrial operations (leather tanning, electroplating, paint and pigment production etc.) because of its hardness and stability. It is found in industrial effluents in concentrations much above the prescribed limit of the World Health Organization (50 µg/L). Detection and remediation of chromium has been the subject of research of many scientists but many previous review works have been insufficient in comprehensive information. This review conveys the basic knowledge of chromate toxicity leading to physical discomfort and sometimes life-threatening illness including irreversible damage to the vital body system in humans. Conventional methods for removing toxic chromium ions (by chemical reduction followed by precipitation, ion- exchange and adsorption on activated coal, alum, kaolinite and ash) are costly for large-scale treatment. Microbial uptake followed by reduction of toxic Cr (VI) has become very successful due to its cost-effectiveness and use as a non-toxic agent. This is referred to as bioremediation. This review emphasises various strategies for hexavalent chromium bioremediation from contaminated water. This review article, therefore, tries to highlight this aspect of bioremediation of Cr (VI) from industrial effluents by native, indigenously resident chromate-resistant bacteria.

Isolation and characterization of hexavalent chromium-tolerant endophytic bacteria inhabiting Solanum virginicum L. roots: A study on potential for chromium bioremediation and plant growth promotion

Present study was performed with the aim to isolate Heavy metal Tolerant- PGPB (HMT-PGPB) from metal-contaminated site and use them for Cr bioremediation. Six different bacterial strains were obtained from the endosphere of Solanum virginicum L. roots and cultured using nutrient agar media amended with 20 mg/L of Cr(VI). The ability of these Cr(VI) tolerant bacterial isolates were assessed for PGP traits like producing siderophores, indole-3-acetic acid (IAA), and phosphate solubilization. The findings indicated that all of the isolates could produce exopolymeric substances and IAA, five of them could produce siderophores, and three could solubilize phosphate. Furthermore, the minimum inhibitory concentrations of these strains werealso determined. These strains were identified as Bacillus licheniformis SxR1, B. tequilensis SxR2, B. subtilis SxR3, B. velezensis SxR4, B. amyloliquefaciens SxR6, and B. stercoris SxR8. To validate the findings, it is crucial to comprehend how Cr(VI) affects Bacillus sp. SxR1 cells to determine the course of uptake and bacterial cell alteration, which was assessed via Fourier Transform-Infrared Spectroscopy (FT-IR) and Scanning Electron Microscopy (SEM).

Enhanced bioremediation of hexavalent chromium via Stenotrophomonas acidaminiphila 4–1 assisted with agricultural wastes-derived biochar

Chromium (Cr) contamination in soil poses high toxicity risks to organisms. In this study, a Cr(VI)-resistant strain was isolated from oil-contaminated soil and designated as Stenotrophomonas acidaminiphila 4–1. The optimal removal efficiency of Cr(VI) (67.4 %) was achieved by employing the response surface methodology, with a glucose concentration of 6.1 %, soil moisture content of 31 %, inoculation dose of 4.5 mL, and initial Cr(VI) concentration of 0.2 mg·g−1. The strain 4–1 was immobilized in biochar derived from the pyrolysis of agricultural waste, including corn straw, loofah, and reed straw. In the loofah biochar-4–1 group, the removal efficiency of Cr(VI) was 74.94 % when the initial concentration of Cr(VI) was 0.2 mg·g−1. The biochar-immobilized strain 4–1 exhibited superior removal efficiency and tolerance towards Cr(VI) compared to the single free strain 4–1.The FT-IR results revealed that the surface functional groups of reed straw biochar exhibited a higher abundance compared to those of corn straw biochar and loofah biochar. The predominant form of Cr(VI) in untreated soil was found to be residual form, while the proportion of Fe-Mn oxides form increased from 7.9 % to 18.8 % within a span of 14 days. Notably, loofah biochar-4–1 exhibited the ability to convert unstable chromium species into stable forms within the soil. This work offers a specific instructive method to for remediating Cr polluted sites.

Molecular approaches for hexavalent chromium bioremediation: Stanford Medical Center

Molecular approaches for hexavalent chromium bioremediation: Stanford Medical Center

Bioremediation of Chlorate and Chromium in Soil Columns Using Contaminated Site Native Culture

AbstractChlorate and hexavalent chromium (chromate) are both widely used in different industries, and the improper waste management in the past left many sites with elevated concentrations in groundwater that pose potential risk to human and/or ecological health. Bioremediation is a sustainable management solution that can reduce both of these contaminants to less toxic species. In our earlier microcosms experiments, we have demonstrated that native microorganisms collected from a site contaminated with chlorate and chromate can lower the concentration of these chemicals in groundwater to acceptable regulatory levels provided sufficient electron donor, nitrogen, and phosphorous are provided. In this study, continuous flow column experiments were performed using soil from the site impacted by both chlorate and chromate in the Province of Manitoba (Canada) and synthetic groundwater amended with acetate, nitrogen, and phosphorous. The objective was to evaluate at a bench scale possibility of in‐situ groundwater treatment. Concentrations of chromate and chlorate measured in the columns' effluent water dropped by 86% and 96%, respectively. However, increased biomass and precipitation of trivalent chromium reduced the water flow rate in the columns, a concern for implementing this method as a long‐term in‐situ remediation solution.

Isolation and identification of a new Bacillus glycinifermentans strain from date palm rhizosphere and its effect on barley seeds under heavy metal stress.

Soil contamination by heavy metals is one of the major problems that adversely decrease plant growth and biomass production. Inoculation with the plant growth-promoting rhizobacteria (PGPR) can attenuate the toxicity of heavy metals and enhancing the plant growth. In this study, we evaluated the potential of a novel extremotolerant strain (IS-2T) isolated from date palm rhizosphere to improve barley seedling growth under heavy metal stress. The species-level identification was carried out using morphological and biochemical methods combined with whole genome sequencing. The bacterial strain was then used in vitro for inoculating Hordeum vulgare L. exposed to three different Cr, Zn, and Ni concentrations (0.5, 1, and 2mM) in petri dishes and different morphological parameters were assessed. The strain was identified as Bacillus glycinifermentans species. This strain showed high tolerance to pH (6-11), salt stress (0.2-2M), and heavy metals. Indeed, the minimum inhibitory concentrations at which bacterium was unable to grow were 4mM for nickel, 3mM for zinc, more than 8mM for copper, and 40mM for chromium, respectively. It was observed that inoculation of Hordeum vulgare L. under metal stress conditions with Bacillus glycinifermentans IS-2T stain improved considerably the growth parameters. The capacity of the IS-2T strain to withstand a range of abiotic stresses and improve barley seedling development under lab conditions makes it a promising candidate for use as a PGPR in zinc, nickel, copper, and chromium bioremediation.

A COMPARATIVE STUDY OF THE WATER QUALITY BEFORE AND AFTER TREATMENT OF CONTAMINATED WATER USING THE PEELS OF MUSA PARASIDIACA IN RELATION TO SEASONAL VARIATION

Chromium contamination can alter genetic materials and cause hazardous health effect in life. Bio absorption method relies on the ability of biological materials to remove the heavy metals by binding metal in various ways. The bio-adsorbents consist of dead and metabolically inactive cells. The residues of banana peels can be processed and converted to be adsorbents because they have large surface areas, high swelling capacities, excellent mechanical strengths, and are convenient to use and have great potential to adsorb harmful contaminants such as heavy metals. In the present study, contaminated water was treated using the powdered peels of Musa parasidiaca, then the physico-chemical factors and the amount of chromium before and after treatment were compared in relation to winter and summer. The amount of heavy metal chromium concentration was reduced drastically. Based on the results obtained the peels of Musa parasidiaca is proved to be a low cost and effective bio-adsorbent in bioremediation of chromium.

Bioremediation of Hexavalent Chromium By Bacteria Isolated From Buriganga River, Dhaka City

Environmental pollution due to hexavalent chromium (Cr6+) is widespread because of the anthropogenic activities in various industrial processes, notably in leather tanning. Hexavalent chromium (Cr6+) is considered as highly toxic, carcinogenic, and mutagenic due to its high solubility in water, interaction with cellular proteins, and biological membrane permeability. Trivalent chromium (Cr3+), on the other hand, is less water-soluble, and relatively benign in nature. Thus, bioreduction of toxic Cr6+ to relatively non-toxic Cr3+ by microorganisms can be an inexpensive and eco-friendly option for chromium bioremediation. In this regard, the present study attempted to isolate chromium-reducing bacteria from Buriganga River in order to assess their capability for chromium bioremediation. Ten chromium-tolerating bacterial isolates were successfully identified. The results revealed that these isolates, particularly strains of Bacillus subtilis, exhibited a remarkable ability to remove up to 89% of hexavalent chromium from the contaminated medium within three days of incubation.
 Stamford Journal of Microbiology, 2023. Vol. 13, Issue 1, p. 25-29

Docking assisted mechanistic elucidation of bio conversion of hexavalent chromium by Serratia marcescens AJRR-22 that is effective yet long term sustainable in bio-geosphere

Environmental accumulation of hexavalent chromium [Cr(VI)] in the food chain can induce detrimental effects on plants and animals, which calls for effective remediation strategies using biological entities. The bacterium isolated from an iron mine in Odisha, India, is identified asSerratia marcescensAJRR-22. This multi-metal tolerant strain is capable of bio-converting up to 350 mg/L Cr(VI) within 72 h of incubation. Observable electron dense precipitates in transmission electron microscopic images, data patterns in fluorescence microscopy and flow cytometry clearly reveal the chromate reduction ability of the strain. The molecular study is depicted by X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopic analyses. Furthermore, a simulation study to estimate the interactions of chromium bound flavin reductasewith predicted docked complexes suggests significant negative Gibbs free energy and a low inhibition constant (Ki), signifying strong spontaneous binding of Cr(VI) to the enzyme, which makes the strain an efficient candidate for chromium bioremediation.

Algae from Cr-containing infiltrate bioremediation for valorised chemical production – Seasonal availability, composition, and screening studies on hydrothermal conversion

Integrating bioremediation of toxic wastewater with value-added production is increasing interest, but - due to some essential problems - it is hardly applied in industrial practice. The aim of the study was an annual observation of the taxonomic and biochemical composition of various Cr-resistant algal communities grown in the existing Cr-containing infiltrate treatment system, selection of the most suitable algal biomass for infiltrates bioremediation and chromium-loaded algae conversion under mild subcritical conditions. Considering continuous availability and relatively constant chemical composition, Cladophora sp. was selected for utilisation in the chromium bioremediation system, simultaneously as a waste biomass source suitable for hydrothermal conversion. Screening studies conducted in a continuous pilot plant confirmed the possibility of selective extraction of saccharides and their separation from the metals remaining in the solid residual. The negligible concentration of metals in the obtained sugar-rich aqueous phase is essential for its further use in biotechnological processes.

Isothermal and Kinetics Modeling Approach for the Bioremediation of Potentially Toxic Trace Metal Ions Using a Novel Biosorbent Acalypha wilkesiana (Copperleaf) Leaves.

The presence of trace metals in wastewater brings serious environmental pollution that threatens human health as well as the ecosystem throughout the world due to their non-biodegradability nature. The present study focuses on the bioremediation of toxic trace metals, namely arsenic (As), cadmium (Cd), and chromium (Cr), using Acalypha wilkesiana leaf raw biomass. The optimization of various process variables was done to determine the removal percentage of trace metal using Acalypha wilkesiana leaf raw biomass, and the optimum conditions were an adsorbent dose of 0.5g, contact time 10h, 8h, and 10h, process temperature 30°C, initial concentration of trace metal as 30µg/L, 30mg//L, and 40mg/L, and pH of 7.5, 7 and 7.5 for As5+, and Cd2+ and Cr6+, respectively. Acalypha wilkesiana leaf raw biomass is characterized using a scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), and Fourier transformation infrared spectroscopy (FTIR), zeta potential before and after adsorption of the trace metal ions. The study was well fitted for the equilibrium data for Langmuir isotherm for As5+, Cd2+, and Cr6+, Freundlich for As5+, Dubinin-Radushkevinch (D-R) for Cr6+, and Temkin for As5+ and Cr6+. The adsorption of all three trace metals was confirmed by the kinetics and thermodynamic studies to be following pseudo-second-order kinetics with endothermic as well as spontaneous processes, respectively. Thus, the present study indicates Acalypha wilkesiana leaf raw biomass as an effective and efficient novel biosorbent to remediate different trace metals from aqueous systems with its possible application in existing and novel methods for wastewater management.

In Silico Comparative Metagenomic Analysis of Microbial Communities of Chromium Contaminated Sites

Chromium is one of the highly toxic and carcinogenic heavy metals. Due to increased anthropogenic activities, high concentration of chromium is found in many areas. Many microorganisms have the ability to detoxify chromium. Metagenomics allow us to comprehensively study microbial communities present at different sites without culturing them. The objective of this study was to analyze the abundance of microbial groups in different environments contaminated with chromium. For this purpose, chromium contaminated soil, anaerobic sludge and reactor samples were chosen. 16S rRNA data of these samples was retrieved from NCBI SRA database. The sequences were analyzed by Mothur software accessed via Galaxy server, and were classified using SILVA database. Venn diagram, phylogenetic tree, heatmap, relative abundance graphs and Krona pie charts were generated. Statistical analysis was also performed in the form of AMOVA and HOMOVA tests. According to results of our study, Proteobacteria, Leucobacter, Actinomycetales, Actinobacteria, Arthrobacter, Rhizobiales, Sphingomonas, Bradyrizobium and Nucardioidaceae were present in all the samples. Firmicutes, Planctomycetes, Verrucomicrobia and Bacteroidetes were more abundant in chromium contaminated samples as compared to control samples. The results were also found to be statistically significant. The above-mentioned bacteria can be targeted and studied to discover their roles in bioremediation of chromium contaminated sites.

Microorganisms from tannery wastewater: Isolation and screening for potential chromium removal

Chromium is a chemical element that enables many industries to function. However, its hexavalent form can cause serious problems. The current methods used to remove Cr are expensive and cause environmental damages, hence the need to set up the most environment friendly methods like the biological methods. The main objectives of this study were isolation, characterization of hexavalent chromium removing microorganisms from Marrakech tannery wastewater. Four microbial strains namely Bacillus licheniformis, Bacillus megaterium, Byssochlamys sp. and Candida maltosa were selected and identified using molecular methods. Candida maltosa and Byssochlamys sp. produce antimicrobial metabolites that have a microbiostatic effect. Bacillus licheniformis, Bacillus megaterium and Candida maltosa removed 92.75; 75.48 and 43.27% of hexavalent chromium at the concentration of 50 mg/L in 96 h respectively. In contrast, Byssochlamys sp. removed 100% of 50 mg/L of hexavalent chromium concentration in 72 h. At 100 mg/L of hexavalent chromium, it was recorded that Bacillus licheniformis, Bacillus megaterium, Byssochlamys sp., Candida maltosa, consortium C reduced 41.20; 50.88; 64.44; 31.88; 57.30% in 96 h respectively. Byssochlamys sp. strain could be the best candidate for bioremediation of chromium contaminated leather industry effluent and metal recovery in mining process.

Mesorhizobium improves chickpea growth under chromium stress and alleviates chromium contamination of soil

Environmental pollution has become a transnational issue that impacts ecosystems, soil, water, and air and is directly related to human health and well-being. Chromium pollution decreases the development of plant and microbial populations. It warrants the need to remediate chromium-contaminated soil. Decontaminating chromium-stressed soils via phytoremediation is a cost-effective and environmentally benign method. Using multifunctional plant growth-promoting rhizobacteria (PGPR) lower chromium levels and facilitates chromium removal. PGPR work by altering root architecture, secreting chemicals that bind metals in the rhizosphere, and reducing phytotoxicity brought on by chromium. The present study aimed to investigate the chromium bioremediation capacity of metal-tolerant PGPR isolate while promoting the growth of chickpeas in the presence of varying levels of chromium (15.13, 30.26, and 60.52 mg/kg of chromium). The isolate, Mesorhizobium strain RC3, substantially reduced chromium content (60.52 mg/kg) in the soil. It enhanced the root length by 10.87%, the shoot length by 12.38%, the number of nodules by 6.64%, and nodule dry weight by 13.77% at 90 days. After 135 days of sowing, more improvement in the root length (18.05), shoot length (21.60%)the chlorophyll content (6.83%), leghaemoglobin content (9.47%), and the highest growth in the crop seed yield (27.45%) and crop protein content (16.83%)The isolate reduced chromium accumulation in roots, shoots, and grains chickpea. Due to chromium bioremediation and its plant growth-promoting and chromium-attenuating qualities, Mesorhizobium strain RC3 could be used as a green bioinoculant for plant growth promotion under chromium stress.