of 6.3 W/m
3 (Hou et al. 2016). Similarly, Cui et al. (2014) used microalgae as a
substrate in the anodic chamber of MFC, which achieved a maximum power output
of 1.9 W/m
2 . Luimstra et al. (2014) investigated photosynthetic electrogenic activity
in algae and cyanobacteria by incorporating photosynthetic species in the anodic
chamber of MFC, producing a power output of 6.2 mW/m
2 . Rapid degradation of
dyes, which has high redox potential such as azo dyes, was possible in the anodic
chamber of MFC (Fernando et al. 2014). Khan et al. (2015) reported the effective
degradation of azo dye, using an anaerobic-aerobic process in a single-chamber
MFC. Degradation of xenobiotic compounds, like refractory organic pesticides (Cao
et al. 2015), and phenanthrene and benzene (Adelaja et al. 2017) have also been
successful by MFC.
2.4 Metagenomics and Their Role in Bioremediation
Microorganisms play an important role in numerous processes, including functioning of the ecosystem. There remains a greater challenge in cultivating and understanding microorganisms’ physiology for bioremediation (Overmann et al. 2017).
By 2017, around 400,000 different bacterial and archaea species were predicted to be
identified (Yarza et al. 2014). Yet, there is a lack of characterization of microbial
communities in contaminated sites due to huge microbial diversity and the challenge
in cultivating them. Approaches such as metagenomics in combination with highthroughput sequencing technologies have revealed the diversity, adaptation, and
evolution of microorganisms prevailing in the contaminated sites. Metagenomics
allows studying the genetic material of microbial populations, by isolating them
directly from environmental samples, and aids in facilitating the process of bioremediation. Metagenomics targets the community profile of individual organisms at
meta-level. As 99% of microbes are uncultivable, which poses a limitation to the
culturable techniques (Dickson et al. 2014; Bursle and Robson 2016), metagenomics
aims to overcome this limitation.
Meta-omics technologies, such as metaproteomics and metatranscriptomics, have
developed over the years and play a pivotal role in diversified applications (Dubey
et al. 2020). Metatranscriptomics involves the analysis of metagenomic mRNA,
which provides information about gene expression profiles of complex microbial
communities present in the environmental sample. There is a huge significance of
metatranscriptomics studies, as it can strengthen the results obtained through
metagenomics and investigate the gene activity within a specified environmental
condition. Metaproteomics involves an analysis of all the protein samples from
environmental sources. In a study, microbial diversity and metaproteomic analysis
of activated sludge showed Burkholderiales populations have better degradation
ability for polycyclic aromatic hydrocarbons and their increase in activated sludge
helps improve the degradation performance of naphthalene (Li et al. 2019).
Metabolomic approaches have helped to analyze the potential metabolite profiles
of microorganisms. However, the data generated by metabolomics differs
11 Modern Bioremediation Approaches for Clean and Green Environment
229
3 (Hou et al. 2016). Similarly, Cui et al. (2014) used microalgae as a
substrate in the anodic chamber of MFC, which achieved a maximum power output
of 1.9 W/m
2 . Luimstra et al. (2014) investigated photosynthetic electrogenic activity
in algae and cyanobacteria by incorporating photosynthetic species in the anodic
chamber of MFC, producing a power output of 6.2 mW/m
2 . Rapid degradation of
dyes, which has high redox potential such as azo dyes, was possible in the anodic
chamber of MFC (Fernando et al. 2014). Khan et al. (2015) reported the effective
degradation of azo dye, using an anaerobic-aerobic process in a single-chamber
MFC. Degradation of xenobiotic compounds, like refractory organic pesticides (Cao
et al. 2015), and phenanthrene and benzene (Adelaja et al. 2017) have also been
successful by MFC.
2.4 Metagenomics and Their Role in Bioremediation
Microorganisms play an important role in numerous processes, including functioning of the ecosystem. There remains a greater challenge in cultivating and understanding microorganisms’ physiology for bioremediation (Overmann et al. 2017).
By 2017, around 400,000 different bacterial and archaea species were predicted to be
identified (Yarza et al. 2014). Yet, there is a lack of characterization of microbial
communities in contaminated sites due to huge microbial diversity and the challenge
in cultivating them. Approaches such as metagenomics in combination with highthroughput sequencing technologies have revealed the diversity, adaptation, and
evolution of microorganisms prevailing in the contaminated sites. Metagenomics
allows studying the genetic material of microbial populations, by isolating them
directly from environmental samples, and aids in facilitating the process of bioremediation. Metagenomics targets the community profile of individual organisms at
meta-level. As 99% of microbes are uncultivable, which poses a limitation to the
culturable techniques (Dickson et al. 2014; Bursle and Robson 2016), metagenomics
aims to overcome this limitation.
Meta-omics technologies, such as metaproteomics and metatranscriptomics, have
developed over the years and play a pivotal role in diversified applications (Dubey
et al. 2020). Metatranscriptomics involves the analysis of metagenomic mRNA,
which provides information about gene expression profiles of complex microbial
communities present in the environmental sample. There is a huge significance of
metatranscriptomics studies, as it can strengthen the results obtained through
metagenomics and investigate the gene activity within a specified environmental
condition. Metaproteomics involves an analysis of all the protein samples from
environmental sources. In a study, microbial diversity and metaproteomic analysis
of activated sludge showed Burkholderiales populations have better degradation
ability for polycyclic aromatic hydrocarbons and their increase in activated sludge
helps improve the degradation performance of naphthalene (Li et al. 2019).
Metabolomic approaches have helped to analyze the potential metabolite profiles
of microorganisms. However, the data generated by metabolomics differs
11 Modern Bioremediation Approaches for Clean and Green Environment
229