**7. Bioremediation applications**

*Trace Metals in the Environment - New Approaches and Recent Advances*

consequently, their diversity, abundance and community structure in polluted environments offer insight into the chance of any bioremediation technique providing other environmental factors, which can inhibit microbial activities. Advanced Molecular techniques such as 'Omics' includes genomics, proteomics, metabolomics and transcriptomics have contributed towards microbial identification, functions, metabolic and catabolic pathways, with microbial based methods. Nutrient availability, low population or absence of microbes with degradative capabilities, and pollutant bioavailability may delay the achievement of bioremediation. Since bioremediation depends on microbial process, biostimulation and bioaugmentation approaches speed up microbial activities in polluted sites. Biostimulation increase microbial activities by the addition of nutrients to a polluted sample. Microorganisms are abundantly present in different type of environmental condition, it is noticeable that pollutant degrading microbes are naturally present in polluted contaminated sites, their growth and metabolic activities may depends on pollutant type and concentration; later, we can use of agro-industrial wastes, which contains nitrogen, phosphorus and potassium as a nutrient source most polluted sites. Microbial consortium has been reported to degrade pollutants more efficiently than pure isolates [33]. This activity due to metabolic diversities of individual isolates, which potency create from their isolation source, adaptation process, pollutant composition, and synergistic effects, which may lead to complete and rapid degradation of pollutants when such isolates are mixed together [34]. Additional so, both bioaugmentation and biostimulation were effective in removing pollutant such as polyaromatic hydrocarbons (PAHs) from heavily polluted sample compared to non-amended setup (control) [35].

Although bioaugmentation has recognized effective method, it has been shown to increase the degradation of many compounds. If proper biodegrading microorganisms are not present in soil or if microbial populations decreased because of contaminant toxicity, specific microorganisms can be added as "introduced organisms" to improve the current populations and the possibility that the inoculated microorganisms may not survive in the new environment make bioaugmentation a very uncertain method. This process is known as bioaugmentation. Bioremediation technique in which natural or genetically engineered bacteria with unique metabolic profiles are used to treat sewage or contaminated water or soil. The use of alginate, agar, agarose, gelatin, gellan gum and polyurethane as carrier materials

Biosurfactants are chemical equivalents having ecofriendly and biodegradable properties. However, high construction cost and low scalability application of biosurfactants to polluted site are uneconomical. Agro-industrial wastes combination are nutrient sources for development of biosurfactant producers during fermentation process. Application of several bioremediation techniques will help increase

Enhancing bioremediation ability with organized use of genetically engineered microorganisms (GEM) is a favorable approach. This is due to possibility of engineering a designer biocatalyst target pollutant including recalcitrant compounds by combining a novel and efficient metabolic pathways, widening the substrate range

However, parallel gene transfer and multiplication of GEM in an environmental application are encouraging approach. Bacterial containment systems, in which any

Further, derivative pathway of genetically engineering microorganisms with a target polluted compound using biological approach could increase bioremediation efficiency. Nanomaterials decline the toxicity of pollutant to microorganisms because nanomaterials having increase surface area and lower activation energy,

solve some of the challenges associated with bioaugmentation [36].

of existing pathways and increasing stability of catabolic activity [38].

GEM escaping an environment to reconstruct polluted environment.

which reduce time and cost of bioremediation [39].

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remediation efficiency [37].

Bioremediation must be considered as appropriate methods that can applied to all states of matter in the environment

i.Solids (soils, sediment and sludge)

ii.Liquids (ground water, surface water and industrial waste water

iii.Gases (industrial air emissions)

iv.Sub-surface environments (saturated and vadose zones).

The general approaches to bioremediation are the (i) intrinsic (natural) bioremediation, (ii) biosimulation (environmental modifications, through nutrient application and aeration, and (iii) bioaugmentation (addition of microbes).

The biological community exploited for bioremediation generally consists of the native soil microflora. However, higher plants can also be manipulated to enhance toxicant removal (phytoremediation), especially for remediation of metal contaminated soils.
