This review revealed the interest in processes involving heavy metal uptake by microorganisms has increased considerably in recent years due to the biotechnological potential of micro-organisms in removing and/or recovery of metals. The conventional methods, such as synthetic ion exchangers are considered as mature technologies. Biosorption is still in infant stages, and additional improvements in both performance and costs can be expected. Besides the contributions of the various biosorbents, which are potentially effective and readily available for heavy metal removal. These biosorbents present attractive opportunities as a low-cost means of protecting the environment from pollution. A sustainable approach needs to be developed in order to select the most appropriate biosorbent, operating conditions, and efficient mechanism of heavy metal removal in industrial effluent, to sufficiently address the major challenges involved. Also, in order to develop a reliable biosorption process, more research is needed in biosorbent characterization, in terms of surface morphology and area, zeta potential, functional groups, and particle size, as these are important in biosorption experiments, influenced by the pretreatment of the biosorbents. Biodegradation also a very fruitful and attractive option to remediating, cleaning, managing and recovering techniques for solving polluted environments through microbial activity. In the future in the area researchers should explore novel species that have great potential. The speed of unwanted waste substances degradation is determined in competition within biological agents, inadequate supply with essential nutrient, uncomfortable external abiotic conditions (aeration, moisture, pH, temperature), and low bioavailability of the pollutant. Due to these factors, biodegradation in the natural condition is not more successful leads to be less favorable.
Bioremediation can be effective only where environmental conditions permit microbial growth and activity. Microorganisms and plants possess inherent biological mechanisms that enable them to survive under heavy metal stress and remove the metals from the environment. Bioremediation is measured to be a very safe and obliging technology as it depends on microbes that occur naturally in the soil and pose no hazard to the environment and the people living in that area. The procedure of bioremediation can be simply carried out on-site without initiating a major disruption of normal actions and threats to humans and environment during transportation. Bioremediation is less affluent than other technologies that are used for clean-up of dangerous waste. Even still numerous sources of bioremediation for instance bacteria, archaebacteria, yeasts, fungi, algae, and plants are accessible, but, the biological treatment alone is not adequate enough to treat the pollutants or contaminated sites. A comprehensive study of area wise and pollutant type database is much desirable to finalize the priority area and the need for the operative elimination of the contaminant from the contaminated sites. As regular resources are major assets to humans their adulteration resulted in long term effects of pollution (noise and radiation), global warming, ozone depletion, and greenhouse gases. The sanitization of these natural resources is important for the preservation of nature and the environment using the bioremediation process. Thus, there is a vital need to study the consequence of numerous microorganisms in combination against various pollutants for the preservation of natural resources and environmental management.
Bacteria is one of the greatest vital microbial candidates which needs to be widely explored for the bioremediation ability and though, a few studies have been carried out in the said area, more inclusive and complete studies need to be conceded out for extracting the best out of bacterial systems as “heavy-metal contamination alleviator. However, further research is needed to investigate other beneﬁcial biological methods and mechanisms involved in remediating heavy metal stress and improving plant growth. Biological fertilizers could be applied by using bacteria and fungi to provide essential nutrients to plant growth. However, more study is needed regarding exact and clear mechanisms involved in the removal of heavy metals by bacteria, fungi, and algae. Metagenomic approaches and metabolic analysis should also be used to study the functional composition of microbial communities within the polluted sites for metal resistance genes that could be used to improve specific heavy metal degradation strains of microbes. Public perception of the use of gene technology for bioremediation will also need to change for its effective utilization; this will require cooperation between researchers and environmentalists. Bioremediation is not a new technique, but as our knowledge of the underlying microbial reactions grows, our ability to use them to our advantage increases. Frequently, bioremediation requires fewer resources and less energy than conventional technology and doesn’t accumulate hazardous by-products as waste. Bioremediation has technical and cost advantages, although it can often take more time to carry out than traditional methods. Bioremediation can be tailored to the needs of the polluted site in question and the specific microbes needed to break down the pollutant are encouraged by selecting the limiting factor needed to promote their growth. This tailoring may be further improved by using synthetic biology tools to pre-adapt microbes to the pollution in the environment to which they are to be added