Current Eco-friendly and Sustainable Methods for Heavy Metals Remediation of Contaminated Soil and Water: Special Emphasis on Use of Genetic Engineering and Nanotechnology

Document Type : Review Paper

Authors

1 Department of Zoology, Maitreyi College, University of Delhi, Delhi, India

2 Department of Zoology, Gargi College, University of Delhi, Delhi, India

Abstract

Anthropogenic activities have polluted soil and aquatic ecosystems by introducing harmful heavy metals (HMs) such as cadmium, copper, mercury, lead, manganese, nickel, zinc, and others. These HMs lead to serious health conditions in humans like cancer, skin lesions, birth defects, liver and kidney damage, and mental retardation leading to other disabilities. Conventional methods of HM remediation of contaminated soil and water include physical, chemical, biological, and integrated methods. The use of physical and chemical methods, in isolation, has been reduced in practice, owing to their negative impacts, however, work on suitable integrated approaches, and the use of organisms for HM remediation has been in steady progress since past few decades. These approaches have proved to be eco-friendly, cost-effective, and show reduced negative impacts on the environment and biota. However, there is consistent increase in anthropogenic contribution to this problem, so, to keep pace with it, more recently work is in advancement on exploiting the biological system to increase the efficiency of bioremediation, using the latest technologies such as genetic engineering and nanotechnology. This paper provides an overview of the current methods deployed to address this problem, developments made in this field in past few decades, and evokes a research thrust that might lead to novel remediation approaches in the future.

Keywords

Main Subjects


Ackerley, D. F., Gonzalez, C. F., Keyhan, M., Blake, R. & Matin, A. (2004). Mechanism of chromate reduction by the Escherichia coli protein, NfsA, & the role of different chromate reductases in minimizing oxidative stress during chromate reduction. Environ. Microbiol., 6(8), 851–860. https://doi.org/10.1111/j.1462-2920.2004.00639.x 
Adenigba, V. O., Omomowo, I. O., Oloke, J. K., Fatukasi, B. A., Odeniyi, M. A. & Adedayo, A. A. (2020). Evaluation of microalgal-based nanoparticles in the adsorption of heavy metals from wastewater. In IOP Conf. Ser.: Mater. Sci. Eng., 805(1), 012030. DOI 10.1088/1757-899X/805/1/012030.
Ahmed, E., Abdulla, H. M., Mohamed, A. H. & El-Bassuony, A. D. (2016). Remediation & recycling of chromium from tannery wastewater using combined chemical–biological treatment system. Process Saf. Environ. Protect., 104, 1–10. https://doi.org/10.1016/j.psep.2016.08.004 
Akhtar, F. Z., Archana, K.  M., Krishnaswamy, V.G. & Rajagopal, R. (2020). Remediation of heavy metals (Cr, Zn) using physical, chemical & biological methods: a novel approach. SN Appl. Sci., 2, 267. https://doi.org/10.1007/s42452-019-1918-x
Al-Homaidan, A. A., Al-Ghanayem, A. A. & Areej, A. H. (2011). Green algae as bioindicators of heavy metal pollution in wadi hanifah stream, Riyadh, Saudi Arabia. Int. J. Water Res. Arid Environ., 1(1), 10-15.
Ali, M. M., Hossain, D., Al-Imran, Khan, M. S., Begum, M. & Osman, M. H. (2021). Environmental Pollution with Heavy Metals: A Public Health Concern, Heavy Metals - Their Environmental Impacts & Mitigation, Mazen Khaled Nazal & Hongbo Zhao, IntechOpen, DOI: 10.5772/intechopen.96805. Available from: https://www.intechopen.com/chapters/76739 
Almaguer-Cantú, V., Morales-Ramos, L. H. & Balderas-Renteria, I. (2011). Biosorption of lead (II) & cadmium (II) using Escherichia coli genetically engineered with mice metallothionein. Water Sci. Technol., 63(8), 1607-1613. https://doi.org/10.2166/wst.2011.225 
Aragaw, T. A., Bogale, F. M. & Aragaw, B. A. (2021). Iron-based Nanoparticles in Wastewater Treatment: A Review on Synthesis Methods, Applications, & Removal Mechanisms. J. Saudi Chem. Soc., 25, 101280. https://doi.org/10.1016/j.jscs.2021.101280 
Ayangbenro, A. S. & Babalola, O. O. (2017). A new strategy for heavy metal polluted environments: A review of microbial biosorbents. Int. J. Environ. Res. Public Health, 14, 94. https://doi.org/10.3390/ijerph14010094 
Azhar, A. T. S., Nabila, A. T. A., Nurshuhaila, M. S., Shaylinda, M. Z. N. & Azim, M. A. M (2016). Electromigration of contaminated soil by electrobioremediation technique. Soft soil engineering international conference, 2015 (SEIC2015), IOP Publishing IOP Conf. Series. Mater. Sci. Engg., 136, 1–5. DOI 10.1088/1757-899X/136/1/012023.
Bakulski, K. M., Seo, Y. A., Hickman, R. C., Brandt, D., Vadari, H. S., Hu, H. & Park, S. K. (2020). Heavy Metals Exposure & Alzheimer’s Disease & Related Dementias. J. Alzheimer’s Dis., 76(4), 1215–1242. https://doi.org/10.3233/JAD-200282
Balali-Mood, M., Naseri, K., Tahergorabi, Z., Khazdair, M. R. & Sadeghi, M. (2021). Toxic Mechanisms of Five Heavy Metals: Mercury, Lead, Chromium, Cadmium, & Arsenic. Front. Pharmacol., 12, 643972. https://doi.org/10.3389/fphar.2021.643972 
Bang, S. W., Clark, D. S. & Keasling, J. D. (2000). Engineering hydrogen sulphide production & cadmium removal by expression of the thiosulfate reductase gene (phs ABC) from Salmonella enterica serovar typhimurium in Escherichia coli. Appl. Environ. Microbiol., 66(9), 3939-3944. https://doi.org/10.1128/aem.66.9.3939-3944.2000 
Bhargavi, V. L. N. & Sudha, P. N. (2015). Removal of heavy metal ions from soil by electrokinetic assisted phytoremediation method. Int. J. ChemTech Res., 8, 192–202.
Bhuiyan, M. S. U., Min, S. R., Jeong, W. J., Sultana, S., Choi, K. S., Lee, Y. & Liu, J. R. (2011). Overexpression of AtATM3 in Brassica juncea confers enhanced heavy metal tolerance & accumulation. Plant Cell Tissue Organ Cult., 107(1), 69–77. https://doi.org/10.1007/s11240-011-9958-y 
Bittsanszkya, A., Kömives, T., Gullner, G., Gyulai, G., Kiss, J., Heszky, L., Radimszky, L. & Rennenberg, H. (2005). Ability of transgenic poplars with elevated glutathione content to tolerate zinc (2+) stress. Environ. Int., 31(2), 251–254. https://doi.org/10.1016/j.envint.2004.10.001 
Briffa, J., Sinagra, E. & Blundell, R. (2020). Heavy metal pollution in the environment & their toxicological effects on humans. Heliyon, 6(9), e04691. https://doi.org/10.1016/j.heliyon.2020.e04691 
Brim, H., Venkateshwaran, A., Kostandarithes, H. M., Fredrickson, J. K. & Daly, M. J. (2003). Engineering Deinococcus geothermalis for bioremediation of high temperature radioactive waste environments. App. Environ. Microbiol., 69(8), 4575–4582. https://doi.org/10.1128%2FAEM.69.8.4575-4582.2003 
Cheng, H., Yang, B., Ke, T., Li, S., Yang, X., Aschner, M. & Chen, P. (2021). Mechanisms of Metal-Induced Mitochondrial Dysfunction in Neurological Disorders. Toxics, 9(6), 142. https://doi.org/10.3390%2Ftoxics9060142      
Cherian, S. & Oliveira, M. M. (2005). Transgenic Plants in Phytoremediation: Recent Advances & New Possibilities. Environ. Sci. Technol., 39(24), 9377-9390. https://doi.org/10.1021/es051134l  
Chibuike, G. U. & Obiora, S. C. (2014). Heavy Metal Polluted Soils: Effect on Plants & Bioremediation Methods. Appl. Environ Soil Sci., Article ID 752708. https://doi.org/10.1155/2014/752708 
Dangi, A. K., Sharma, B., Hill, R. T. & Shukla, P. (2018). Bioremediation through microbes: systems biology & metabolic engineering approach. Crit. Rev. Biotechnol., 39(1), 79-98. https://doi.org/10.1080/07388551.2018.1500997
Das, N., Bhattacharya, S. & Maiti, M. K. (2016). Enhanced cadmium accumulation & tolerance in transgenic tobacco overexpressing rice metal tolerance protein gene OsMTP1 is promising for phytoremediation. Plant Physiol. Biochem., 105, 297–309. https://doi.org/10.1016/j.plaphy.2016.04.049  
Deng, X. & Jia, P. (2011). Construction & characterization of a photosynthetic bacterium genetically engineered for Hg2+ uptake. Bioresour. Technol., 102(3), 3083–3088. https://doi.org/10.1016/j.biortech.2010.10.051 
Diep, P., Mahadevan, R. & Yakunin, A. F. (2018) Heavy metal removal by bioaccumulation using genetically engineered microorganisms. Front. Bioeng. Biotechnol., 6, 157. https://doi.org/10.3389/fbioe.2018.00157
Divya, B. & Deepak Kumar, M. (2011). Plant-Microbe interaction with enhanced bioremediation. Res. J. BioTechnol., 6:72–79.
Dixit, R., Wasiullah, Malaviya, D., Pandiyan, K., Singh, U. B., Sahu, A., Shukla, R., Singh, B. P., Rai, J. P., Sharma, P. K., Lade, H. & Paul, D. (2015). Bioremediation of Heavy Metals from Soil & Aquatic Environment: An Overview of Principles & Criteria of Fundamental Processes. Sustainability, 7(2), 2189-2212. https://doi.org/10.3390/su7022189 
Doty, S. L., Shang, T. Q., Wilson, A. M., Tangen, J., Westergreen, A. D., Newman, L. A., Str&, S. E. & Gordon, M. P. (2007). Enhanced metabolism of halogenated hydrocarbons in transgenic plants contain mammalian P450 2E1. Proc. Natl. Acad. Sci. USA, 97, 6287–6291. https://doi.org/10.1073%2Fpnas.97.12.6287 
Duran, N., Marcato, P. D., Alves, O. L., Da Silva, J. P. S., De Souza, G. I. H., Rodrigues, F.A. & Esposito, E. (2010). Ecosystem protection by effluent bioremediation, Silver nanoparticles impregnation in a textile fabrics process. J. Nanopart. Res., 12, 285–292. https://doi.org/10.1007/s11051-009-9606-1 
Elyamine, A. M., Moussa, M. G., Ismael, M. A., Wei, J., Zhao, Y., Wu, Y. & Hu, C. (2018). Earthworms, Rice Straw, & Plant Interactions Change the Organic Connections in Soil & Promote the Decontamination of Cadmium in Soil. Int. J. Environ. Res. Public Health, 15(11), 2398. https://doi.org/10.3390/ijerph15112398 
Emenike, C. U., Agamuthu, P. & Fauziah, S. H. (2016). Blending Bacillus sp., Lysinibacillus sp. & Rhodococcus sp. for optimal reduction of heavy metals in leachate contaminated soil. Environ. Earth Sci., 75(1), 26. https://doi.org/10.1007/s12665-015-4805-9 
Emurotu, J. E. & Onianwa, P. C. (2017). Bioaccumulation of heavy metals in soil & selected food crops cultivated in Kogi State, north central Nigeria. Environ. Syst. Res. 6, 21. https://doi.org/10.1186/s40068-017-0098-1 
Engwa, G. A., Ferdinand, P. U., Nwalo, F. N. & Unachukwu, M. N. (2019). Mechanism & Health Effects of Heavy Metal Toxicity in Humans, Poisoning in the Modern World - New Tricks for an Old Dog? Ozgur Karcioglu & Banu Arslan, IntechOpen, DOI: 10.5772/intechopen.82511. Available from: https://www.intechopen.com/chapters/64762 
Gaitán-Solís, E., Taylor, N. J., Siritunga, D., Stevens, W. & Schachtman, D. P. (2015). Overexpression of the transporters AtZIP1 & AtMTP1 in cassava changes zinc accumulation & partitioning. Front. Plant Sci., 6, 492. https://doi.org/10.3389/fpls.2015.00492 
Giri, A. K., Patel, R. K. & Mishra, P. C. (2012). Biosorption of As(V) from aqueous solutions by living cells of Bacillus cereus. Water Sci. Technol., 66(8), 1699–1707. https://doi.org/10.2166/wst.2012.332 
Gogada, R., Singh, S. S., Lunavat, S. K., Pamarthi, M. M., Rodrigue, A., Vadivelu, B., Phanithi, P.-B., Gopala, B. & Apte, S. K. (2015). Engineered Deinococcus radiodurans R1 with NiCoT genes for bioremoval of trace cobalt from spent decontamination solutions of nuclear power reactors. Appl. Microbiol. Biotechnol., 99, 9203–9213. https://doi.org/10.1007/s00253-015-6761-4 
Gordon, J. J. & Quastel, J. H. (1948). Effects of organic arsenicals on enzyme systems. Biochem. J., 42(3), 337-350.
Gosavi, K., Sammut, J., Gifford, S. & Jankowski, J. (2004). Macroalgal biomonitors of trace metal contamination in acid sulfate soil aquaculture ponds. Sci. Total Environ., 324(1-3), 25–39. https://doi.org/10.1016/j.scitotenv.2003.11.002 
Gullner, G., Kömives, T. & Rennenberg, H. (2001).  Enhanced tolerance of transgenic poplar plants overexpressing gamma-glutamylcysteine synthetase towards chloroacetanilide herbicides. J. Exp. Bot., 52(358), 971–979. https://doi.org/10.1093/jexbot/52.358.971 
Ha, C., Zhu, N., Shang, R., Shi, C., Cui, J., Sohoo, I., Wu, P. & Cao, Y. (2016). Biorecovery of palladium as nanoparticles by Enterococcus faecalis & its catalysis for chromate reduction. Chem. Eng. J., 288, 246–254. https://doi.org/10.1016/j.cej.2015.12.015 
Hasin, A. A., Gurman, S. J., Murphy, L. M., Perry, A., Smith, T. J. & Gardiner, P. E. (2010). Remediation of chromium (VI) by a methane-oxidizing bacterium. Environ. Sci. Technol., 44, 400–405. https://doi.org/10.1021/es901723c 
Hassan, M. J., Raza, M. A., Rehman, S. U., Ansar, M., Gitari, H., Khan, I., Wajid, M., Ahmed, M., Shah, G. A., Peng, Y. & Li Z. (2020). Effect of Cadmium Toxicity on Growth, Oxidative Damage, Antioxidant Defense System & Cadmium Accumulation in Two Sorghum Cultivars. Plants, 9(11), 1575. https://doi.org/10.3390/plants9111575 
Hazotte, C., Laubie, B., Rees, F., Morel, J. L. & Simonnot, M. O. (2017) A novel process to recover cadmium & zinc from the hyperaccumulator plant Noccaea caerulescens. Hydrometallurgy, 174, 56-65. https://doi.org/10.1016/j.hydromet.2017.09.012 
Henao, S. G. & Ghneim-Herrera, T. (2021). Heavy Metals in Soils & the Remediation Potential of Bacteria Associated With the Plant Microbiome. Front. Environ. Sci., 9. https://doi.org/10.3389/fenvs.2021.604216
Hullot, O., Lamy, I., Tiziani, R., Mimmo, T. & Ciadamidaro, L. (2021). The effect of earthworms on plant response in metal contaminated soil focusing on belowground-aboveground relationships. Environ. Pollut., 274, 116499. https://doi.org/10.1016/j.envpol.2021.116499 
Huyer, M. & Page, W. J. (1988). Zn2+ increases siderophore production in Azotobacter vinelandii. Appl. Environ. Microbiol., 54(11), 2625–2631.
Ibañez, S., Talano, M., Ontañon, O., Suman, J., Medina, M. I., Macek, T. & Agostini, E. (2016). Transgenic plants & hairy roots: exploiting the potential of plant species to remediate contaminants. New Biotechnol., 33(5), 625-635. https://doi.org/10.1016/j.nbt.2015.11.008 
Jaishankar, M., Tseten, T., Anbalagan, N., Mathew, B. B., & Beeregowda, K. N. (2014). Toxicity, mechanism & health effects of some heavy metals. Interdiscip. Toxicol., 7(2), 60–72. https://doi.org/10.2478%2Fintox-2014-0009 
Kang, S. H., Singh, S., Kim, J. Y., Lee, W., Mulchandani, A. & Chen, W. (2007). Bacteria metabolically engineered for enhanced phtochelatin production & cadmium accumulation. App. Environ. Microbiol., 73, 6317–6320. https://doi.org/10.1128/aem.01237-07 
Kaonga, C. C., Kosamu, I. B., Lakudzala, D. D., Mbewe, R., Thole, B., Monjerezi, M., Chidya R. C. G., Kuyeli, S. & Sajidu, S. M. I. (2017). A review of heavy metals in soil & aquatic systems of urban & semi-urban areas in Malawi with comparisons to other selected countries. Afr. J. Environ. Sci. Technol., 11, 448–460. https://doi.org/10.5897/AJEST2017.2367 
Kapoor, R. T., Salvadori, M. R., Rafatullah, M., Siddiqui, M. R., Khan, M. A. & Alshareef, S. A. (2021). Exploration of Microbial Factories for Synthesis of Nanoparticles - A Sustainable Approach for Bioremediation of Environmental Contaminants. Front. Microbiol., 12, 658294. https://doi.org/10.3389/fmicb.2021.658294 
Karaca, A. (2004). Effect of organic wastes on the extractability of cadmium, copper, nickel, & zinc in soil. Geoderma, 122(2–4), 297–303. https://doi.org/10.1016/j.geoderma.2004.01.016 
Kim, H. A., Lee, K. Y., Lee, B. T., Kim, S. O. & Kim, K. W. (2012). Comparative study of simultaneous removal of As, Cu, & Pb using different combinations of electrokinetics with bioleaching by Acidithiobacillus ferrooxidans. Water Res., 46, 5591–5599. https://doi.org/10.1016/j.watres.2012.07.044 
Kisielowska, E., Hołda, A. & Niedoba, T. (2010). Removal of heavy metals from coal medium with application of biotechnological methods. Górnictwo I Geoinzynieria, 34, 93–104.
Koźmińska, A., Wiszniewska, A., Hanus-Fajerska, E. & Muszyńska, E. (2018). Recent strategies of increasing metal tolerance & phytoremediation potential using genetic transformation of plants. Plant Biotechnol. Rep., 12, 1–14. https://doi.org/10.1007/s11816-017-0467-2 
Krishnasamy, R. & Wilson, D.B. (2000). Construction & characterization of an E.coli strain genetically engineered for Ni(II) bioaccumulation. Appl. Environ. Microbiol., 66(12), 5383-5386. https://doi.org/10.1128%2Faem.66.12.5383-5386.2000 
Kubiak, J. J., Khankhane, P. J., Kleingeld, P. J. & Lima, A. T. (2012). An attempt to electrically enhance phytoremediation of arsenic contaminated water. Chemosphere, 87(3), 259–264. https://doi.org/10.1016/j.chemosphere.2011.12.048 
Kulkarni, S., Ballal, A. & Apte, S. K. (2013). Bioprecipitation of uranium from alkaline waste solutions using recombinant Deinococcus radiodurans. J. Hazard. Mater., 262, 853–861. https://doi.org/10.1016/j.jhazmat.2013.09.057 
Kumari, V. & Tripathi, A. K. (2020). Remediation of heavy metals in pharmaceutical effluent with the help of Bacillus cereus-based green-synthesized silver nanoparticles supported on alumina. Appl. Nanosci., 10, 1709–1719. https://doi.org/10.1007/s13204-020-01351-9 
Kurniawan, S. B., Ramli, N. N., Said, N. S. M., Alias, J. & Imron, M. F., Abdullah, S. R. S., Othman, A. R., Purwanti, I. F. & Hasan, H. A. (2022). Practical limitations of bioaugmentation in treating heavy metal contaminated soil & role of plant growth promoting bacteria in phytoremediation as a promising alternative approach. Heliyon, 8(4), e08995. https://doi.org/10.1016/j.heliyon.2022.e08995
Li, X., Ren, Z., Crabbe, M., Wang, L. & Ma, W. (2021). Genetic modifications of metallothionein enhance the tolerance & bioaccumulation of heavy metals in Escherichia coli. Ecotoxicol. Environ. Saf., 222, 112512. https://doi.org/10.1016/j.ecoenv.2021.112512
Littera, P., Urík, M., Sevc, J., Kolencík, M., Gardosová, K. & Molnárová, M. (2011). Removal of arsenic from aqueous environments by native & chemically modified biomass of Aspergillus niger & Neosartorya fischeri. Environ. Technol., 32, 1215–1222. https://doi.org/10.1080/09593330.2010.532510 
Liu, D., An, Z., Mao, Z., Ma, L. & Lu, Z. (2015). Enhanced Heavy Metal Tolerance & Accumulation by Transgenic Sugar Beets Expressing Streptococcus thermophilus StGCS-GS in the Presence of Cd, Zn & Cu Alone or in Combination. PloS One, 10(6), e0128824. https://doi.org/10.1371/journal.pone.0128824
Mahanty, S., Chatterjee, S., Ghosh, S., Tudu, P., Gaine, T., Bakshi, M., Das, S., Bhattacharyya, S., Bandyopadhyay, S. & Chaudhuri, P. (2020). Synergistic approach towards the sustainable management of heavy metals in wastewater using mycosynthesized iron oxide nanoparticles: Biofabrication, adsorptive dynamics & chemometric modeling study. J. Water Proces. Eng., 37, 101426. https://doi.org/10.1016/j.jwpe.2020.101426 
Mahar, A., Wang, P., Ali, A., Awasthi, M. K., Lahori, A. H., Wang, Q., Li, R. & Zhang, Z. (2016). Challenges & opportunities in the phytoremediation of heavy metals contaminated soils: A review. Ecotoxicol. Environ. Saf., 126, 111–121. https://doi.org/10.1016/j.ecoenv.2015.12.023 
Mahmoud, A., Al-Qahtani, K. M., Alflaij, S. O., Al-Qahtani, S. F. & Alsamhan, F. A. (2021). Green copper oxide nanoparticles for lead, nickel, & cadmium removal from contaminated water. Sci. Rep., 11(1), 12547. https://doi.org/10.1038/s41598-021-91093-7
Mahmud, H. N. M. E., Huq, A. O. & Binti Yahya, R. (2016). The removal of heavy metal ions from wastewater/aqueous solution using polypyrrole-based adsorbents: a review. RSC Advances, 6(18), 14778-14791. https://doi.org/10.1039/C5RA24358K 
Manzoor, N., Ahmed, T., Noman, M., Shahid, M., Nazir, M. M., Ali, L., Alnusaire, T. S., Li, B., Schulin, R., & Wang, G. (2021). Iron oxide nanoparticles ameliorated the cadmium & salinity stresses in wheat plants, facilitating photosynthetic pigments & restricting cadmium uptake. Sci. Total Environ., 769, 145221. https://doi.org/10.1016/j.scitotenv.2021.145221 
Mao, X., Han, F. X., Shao, X., Guo, K., McComb, J., Arslan, Z. & Zhang, Z. (2016). Electro-kinetic remediation coupled with phytoremediation to remove lead, arsenic & cesium from contaminated paddy soil. Ecotoxicol. Environ. Saf., 125, 16–24. https://doi.org/10.1016/j.ecoenv.2015.11.021 
Masindi, V. & Muedi, K. L. (2018). Environmental Contamination by Heavy Metals. In Heavy Metals, Saleh, H. E.-D. M. & Aglan, R. F. (Eds.). IntechOpen, DOI: 10.5772/intechopen.76082. Available from: https://www.intechopen.com/chapters/60680
Mateos, L. M., Villadangos, A. F., de la Rubia, A. G., Mourenza, A., Marcos-Pascual, L., Letek, M., Pedre, B., Messens, J. & Gil, J. A. (2017). The arsenic detoxification system in corynebacteria: basis & application for bioremediation & redox control. Adv. Appl. Microbiol., 99:103–137. https://doi.org/10.1016/bs.aambs.2017.01.001 
Merlot, S., Hannibal, L., Martins, S., Martinelli, L., Amir, H., Lebrun, M. & Thomine, S. (2014). The metal transporter PgIREG1 from the hyperaccumulator Psychotriagabriellae is a candidate gene for nickel tolerance & accumulation. J. Exp. Bot., 65(6), 1551–1564. https://doi.org/10.1093/jxb/eru025 
Misra, C. S., Sounderajan, S. & Apte, S. K. (2021). Metal removal by metallothionein & an acid phosphatase PhoN, surface-displayed on the cells of the extremophile, Deinococcus radiodurans. J. Hazard Mater., 419, 126477. https://doi.org/10.1016/j.jhazmat.2021.126477 
Mohsenzadeh, F. & Chehregani, R. A. (2012). Bioremediation of heavy metal pollution by nano-particles of Noaea mucronata. Int. J. Biosci. Biochem. Bioinforma., 2, 85–89.
Mohsenzadeh, F. & Rad, A. C. (2011). Application of nano-particles of Euphorbia Macroclada for bioremediation of heavy metal polluted environments. In International Conference on Nanotechnology & Biosensors IPCBEE (Vol. 25).
Muzaffar, S., Khan, J., Srivastava, R., Gorbatyuk, M. S. & Athar, M. (2022). Mechanistic understanding of the toxic effects of arsenic & warfare arsenicals on human health & environment. Cell Biol. Toxicol. https://doi.org/10.1007/s10565-022-09710-8
Nam, S. M., Kim, J. W., Yoo, D. Y., Kim, W., Jung, H. Y., Choi, J. H., Hwang, I. K., Seong, J. K. & Yoon, Y. S. (2016). Effects of aluminum on the reduction of neural stem cells, proliferating cells, & differentiating neuroblasts in the dentate gyrus of D-galactose-treated mice via increasing oxidative stress. J. Vet. Sci., 17(2), 127–136. https://doi.org/10.4142/jvs.2016.17.2.127 
Nguyen, H. T., Yoon, Y., Ngo, H. H. & Jang, A. (2021). The application of microalgae in removing organic micropollutants in wastewater. Crit. Rev. Environ. Sci. Technol., 51(12), 1187–1220. https://doi.org/10.1080/10643389.2020.1753633 
Noman, M., Ahmed, T., Hussain, S., Niazi, M., Shahid, M. & Song, F. (2020). Biogenic copper nanoparticles synthesized by using a copper-resistant strain Shigella flexneri SNT22 reduced the translocation of cadmium from soil to wheat plants. J. Hazard. Mater., 398, 123175. https://doi.org/10.1016/j.jhazmat.2020.123175 
Nwaehiri, U. L., Akwukwaegbu, P. I. & Nwoke, B. E. B. (2020) Bacterial remediation of heavy metal polluted soil & effluent from paper mill industry. Environ. Health Toxicol., 35(2), 1-10. https://doi.org/10.5620%2Feaht.e2020009 
Ojuederie, O. B. & Babalola, O. O. (2017). Microbial & Plant-Assisted Bioremediation of Heavy Metal Polluted Environments: A Review. Int. J. Environ. Res. Public Health, 14(12), 1504. https://doi.org/10.3390%2Fijerph14121504 
Olaniran, A.O., Balgobind, A. & Pillay, B. (2013). Bioavailability of heavy metals in soil: impact on microbial biodegradation of organic compounds & possible improvement strategies. Int. J. Mol. Sci., 14(5), 10197-10228. https://doi.org/10.3390/ijms140510197 
Orłowska, E., Godzik, B. & Turnau, K. (2012). Effect of different arbuscular mycorrhizal fungal isolates on growth & arsenic accumulation in Plantago lanceolata L. Environ. Pollut., 168, 121–130. https://doi.org/10.1016/j.envpol.2012.04.026 
Pasricha, S., Mathur, V., Garg, A., Lenka, S., Verma, K. & Agarwal, S. (2021). Molecular mechanisms underlying heavy metal uptake, translocation & tolerance in hyperaccumulators-an analysis: Heavy metal tolerance in hyperaccumulators. Environ. Chall., 4, 100197. https://doi.org/10.1016/j.envc.2021.100197 
Purwanti, I. F., Kurniawan, S. B., Izzati Ismail, N., Imron, M. F. & Abdullah, S. R. S. (2019). Aluminium removal & recovery from wastewater & soil using isolated indigenous bacteria. J. Environ. Manage., 249, 109412. https://doi.org/10.1016/j.jenvman.2019.109412 
Rahimzadeh RM., Rahimzadeh, RM., Kazemi, S. & Moghadamnia, A. A. (2017). Cadmium toxicity & treatment: An update. Caspian J. Inter. Med., 8(3), 135–145. https://doi.org/10.22088/cjim.8.3.135 
Rai, P. K., Lee, S. S., Zhang, M., Tsang, Y. F. & Kim, K. H. (2019). Heavy metals in food crops: Health risks, fate, mechanisms, & management. Environ. Int., 125, 365–385. https://doi.org/10.1016/j.envint.2019.01.067 
Raidongia, K., Tan, A.T. & Huang, J. (2014). Graphene oxide: some new insights into an old material. In S. Iijima, & K. Tanaka (Eds.), Carbon Nanotubes & Graphene (2 ed.). Elsevier. pp. 341–374.
Raj, K. K., Sardar, U. R., Bhargavi, E., Devi, I., Bhunia, B. & Tiwari, O. N. (2018). Advances in exopolysaccharides based bioremediation of heavy metals in soil & water: A critical review. Carbohydr. Polym., 199, 353-364. https://doi.org/10.1016/j.carbpol.2018.07.037 
Rangabhashiyam, S., Suganya, E., Selvaraju, N. & Varghese, L. A. (2014). Significance of exploiting non-living biomaterials for the biosorption of wastewater pollutants. World J. Microbiol. Biotechnol., 30, 1669–1689. https://doi.org/10.1007/s11274-014-1599-y 
Rodríguez-Llorente, I. D., Lafuente, A., Doukkali, B., Caviedes, M. A. & Pajuelo, E. (2012). Engineering copper hyperaccumulation in plants by expressing a prokaryotic cop C gene. Environ. Sci. Technol., 46(21), 12088–12097. https://doi.org/10.1021/es300842s  
Ruis, O.N. & Daniell, H. (2009).  Genetic engineering to enhance mercury phytoremediation. Curr. Opin. Biotechnol., 20:213–219. https://doi.org/10.1016%2Fj.copbio.2009.02.010 
Samuelson, P., Wernerus, H., Svedberg, M. & Stahl, S. (2000). Staphylococcal surface display of metal-binding polyhistydiyl peptides. Appl. Environ. Microbiol., 66, 1092. https://doi.org/10.1128/aem.66.3.1243-1248.2000 
Saravanan, A., Kumar, S., Ramesh, B. & Srinivasan, S. (2022). Removal of toxic heavy metals using genetically engineered microbes: Molecular tools, risk assessment & management strategies. Chemosphere, 298, 134341. https://doi.org/10.1016/j.chemosphere.2022.134341 
Selvi, A., Rajasekar, A., Theerthagiri, J., Ananthaselvam, A., Sathishkumar, K., Madhavan, J. & Rahman, P. K. (2019) Integrated remediation processes towards heavy metal removal/recovery from various environments- A review. Front. Environ. Sci., 7, 66. https://doi.org/10.3389/fenvs.2019.00066 
Shen, X., Dai, M., Yang, J., Sun, L., Tan, X., Peng, C., Ali, I. & Naz, I. (2022). A critical review on the phytoremediation of heavy metals from environment: Performance & challenges. Chemosphere, 291(Par 3), 132979. https://doi.org/10.1016/j.chemosphere.2021.132979 
Shim, D., Kim, S., Choi, Y. I., Song, W. Y., Park, J., Youk, E. S., Jeong, S.-C., Martinoia, E., Noh, E.-W. & Lee, Y. (2013). Transgenic poplar trees expressing yeast cadmium factor 1 exhibit the characteristics necessary for the phytoremediation of mine tailing soil. Chemosphere, 90(4), 1478–1486. doi: 10.1016/j.chemosphere.2012.09.044. 
Siemianowski, O., Barabasz, A., Kendziorek, M., Ruszczyńska, A., Bulska, E., Williams, L. E. & Antosiewicz, D. M. (2014). AtHMA4 expression in tobacco reduces Cd accumulation due to the induction of the apoplastic barrier. J. Exp. Bot., 65(4), 1125–1139. doi: 10.1093/jxb/ert471. 
Singh, I., Patel, P. B., Sharma, N., Mishra, R. K., Tomar, R. S. & Kaushik, S. (2021). Microbial linkages in the heavy metal remediation. In: Microbiomes & Plant Health: Panoply & their applications. Solanki MK, Kashyap PL, Ansari RA, & Kumari B. (Eds.). Academic Press, Elsevier. Pp 367-395. https://doi.org/10.1016/B978-0-12-819715-8.00013-6 
Singh, S., Anil, A. G., Khasnabis, S., Kumar, V., Nath, B., Adiga, V., Kumar Naik, T., Subramanian, S., Kumar, V., Singh, J. & Ramamurthy, P. C. (2022). Sustainable removal of Cr (VI) using graphene oxide-zinc oxide nanohybrid: Adsorption kinetics, isotherms & thermodynamics. Environ. Res., 203, 111891. https://doi.org/10.1016/j.envres.2021.111891
Singh, Y. & Saxena, M. K. (2022). Insights into the recent advances in nano-bioremediation of pesticides from the contaminated soil. Front. Microbial., 13, 982611. https://doi.org/10.3389/fmicb.2022.982611
Sriprang, R., Hayashi, M., Yamashita, M., Ono, H., Saeki, K. & Murooka, Y. (2002). A novel bioremediation system for heavy metals using the symbiosis between leguminous plant & genetically engineered rhizobia. J. Biotechnol., 99, 279-293. https://doi.org/10.1016/s0168-1656(02)00219-5 
Srivastava, D., Tiwari, M., Dutta, P., Singh, P., Chawda, K., Kumari, M. & Chakrabarty, D. (2021). Chromium Stress in Plants: Toxicity, Tolerance & Phytoremediation. Sustainability, 13, 4629. https://doi.org/10.3390/su13094629 
Tarekegn, M. M., Salilih, F. Z. & Ishetu, A. I. (2020). Microbes used as a tool for bioremediation of heavy metal from the environment. Cogent Food Agricul., 6(1), Article ID1783174. https://doi.org/10.1080/23311932.2020.1783174
Ueda, M. (2016). Establishment of cell surface engineering & its development. Biosci. Biotechnol. Biochem., 80, 1243–1253. doi: 10.1080/09168451.2016.1153953  
Valls, M., Atrian, S., de Lorenzo, V. & La, F. (2000). Engineering a mouse metallothionein on the cell surface of Ralstonia eutropha CH34 for immobilization of heavy metals in soil. Nat. Biotechnol., 18, 661–665. https://doi.org/10.1038/76516 
Van Aken, B., Tehrani, R. & Schnoor, J. (2011). Endophyte-assisted phytoremediation of explosives in poplar trees by Methylobacterium populi BJ001T. In Endophytes of Forest Trees: Biology & Applications, Forestry Sciences. Pirttilä, A.M., Frank, A.C. (Eds.). Springer: Heidelberg, The Netherlands, 80:217–234.
Varia, J., Martínez, S. S., Orta, S. V., Bull, S. & Roy, S. (2013). Bioelectrochemical metal remediation & recovery of Au3+, Co2+ & Fe3+ metal ions. Electrochim. Acta, 95, 125–131. doi: 10.1016/j.electacta.2013.02.051 
Venegas-Rioseco, J., Ginocchio, R. & Ortiz-Calderón, C. (2022). Increase in Phytoextraction Potential by Genome Editing & Transformation: A Review. Plants, 11, 86. https://doi.org/10.3390/plants11010086 
Verma, S., Bhatt, P., Verma, A., Mudila, H., Prasher, P. & Rene, E. R.  (2021). Microbial technologies for heavy metal remediation: effect of process conditions & current practices. Clean Techn. Environ. Policy. https://doi.org/10.1007/s10098-021-02029-8 
Wang, D., Zhang, G., Zhou, L., Wang, M., Cai, D. & Wu, Z. (2017). Synthesis of a Multifunctional Graphene Oxide-Based Magnetic Nanocomposite for Efficient Removal of Cr (VI). Langmuir, 33(28), 7007–7014. https://doi.org/10.1021/acs.langmuir.7b01293 
Wang, X., Zhang, D., Pan, X., Lee, D. J., Al-Misned, F. A., Mortuza, M. G. & Gadd, G. M. (2017). Aerobic & anaerobic biosynthesis of nano-selenium for remediation of mercury contaminated soil. Chemosphere, 170, 266–273. https://doi.org/10.1016/j.chemosphere.2016.12.020 
Wei, Q., Zhang, H., Guo, D. & Ma, S. (2016). Cell Surface Display of Four Types of Solanum nigrum Metallothionein on Saccharomyces cerevisiae for Biosorption of Cadmium. J. Microbiol. Biotechnol., 26(5), 846–853. https://doi.org/10.4014/jmb.1512.12041
White, C., Sharman, A. K. & Gadd G. M. (1998). An integrated microbial process for the bioremediation of soil contaminated with toxic metals. Nature Biotechnol., 16(6), 572–575. https://doi.org/10.1038/nbt0698-572 
Wu, C. H., Wood, T. K., Mulchandani, A. & Chen, W. (2006). Engineering plant-microbe symbiosis for rhizoremediation of heavy metals. Appl. Environ. Microbiol., 72(2), 1129–1134. https://doi.org/10.1128%2FAEM.72.2.1129-1134.2006 
Wu, F. Y., Ye, Z. H. & Wong, M. H. (2009). Intraspecific differences of arbuscular mycorrhizal fungi in their impacts on arsenic accumulation by Pteris vittata L. Chemosphere, 20, 1258–1264. doi: 10.1016/j.chemosphere.2009.05.020
Wu, G., Kang, H., Zhang, X., Shao, H., Chu, L. & Ruan, C. (2010). A critical review on the bio-removal of hazardous heavy metals from contaminated soils: issues, progress, eco-environmental concerns & opportunities. J. Hazard Mater., 174, 1–8. doi: 10.1016/j.jhazmat.2009.09.113
Wuana, R. A. & Okieimen, F. E. (2011). Heavy metals in contaminated soils: a review of sources, chemistry, risks & best available strategies for remediation. Int. Sch. Res. Notices, 2011, 402647. doi: 10.5402/2011/402647  
Yan, A., Wang, Y., Tan, S. N., Mohd Yusof, M. L., Ghosh, S., & Chen, Z. (2020). Phytoremediation: A Promising Approach for Revegetation of Heavy Metal-Polluted L&. Front. Plant Sci., 11, 359. https://doi.org/10.3389/fpls.2020.00359
Yang, L., Wang, J., Yang, Y., Li, S., Wang, T., Oleksake, P., Chrienova, Z., Wu, Q., Nepovimova, E., Zhang, X. & Kuca, K. (2022). Phytoremediation of heavy metal pollution: Hotspots & future prospects. Ecotoxicol. Environ. Saf., 234, 113403. https://doi.org/10.1016/j.ecoenv.2022.113403