8.9 Factor Affecting the Bioremediation
The bioremediation of the polluted environment is a complex process which is
influenced by certain factors such as microbial factors including growth until critical
biomass is reached, mutation and horizontal gene transfer, enzyme induction,
enrichment of the capable microbial populations, and production of toxic metabolites; environmental factors include depletion of preferential substrates, lack of
nutrients, inhibitory environmental conditions viz soil, temperature (Chitara et al.
2017), pH, O 2 and nutrients; substrate factor includes too low concentration of
contaminants, chemical structure of contaminants, toxicity of contaminants, and
solubility of contaminants; biological aerobic vs anaerobic process factor includes
oxidation/reduction potential, availability of e-accepters, and microbial population
present in the site; growth substrate vs co-metabolism factor includes type of
contaminants, concentration, alternate carbon source present, and microbial interaction (competition, succession, and predation); physico-chemical bioavailability of
pollutants include equilibrium sorption, irreversible sorption, and incorporation into
humic matters, and some of the mass transfer limitations are O 2 diffusion and
solubility, diffusion of nutrients, and solubility/miscibility in/with water (Boopathy
2000). The microorganisms are cosmopolitan in nature which can be isolated from
everywhere such as at subzero temperatures, extreme heat, desert conditions, in
water, with an excess of oxygen, and in anaerobic conditions, with the presence of
hazardous compounds or on any waste stream (Boopathy 2000). The microbes
utilize the energy source and carbon source and other biological systems. These
microbes can be used to remediate environmental hazards. Joshi (2018) divided the
microbes into two groups viz. aerobic and anaerobic groups as follows:
8.9.1 Aerobic
This group includes those microbes which exist in the presence of oxygen (Rayu
et al. 2012), e.g., Pseudomonas, Alcaligenes, Sphingomonas, Rhodococcus, and
Mycobacterium. These bacteria are helpful in bioremediation of polluted soil and
are reported to degrade pesticide and hydrocarbon both as well as alkenes
compounds.
8.9.2 Anaerobic
This group includes those microbes which exist in the absence of oxygen (Rayu et al.
2012); for example ligninolytic fungi such as the white-rot fungus Phanaerochaete
chrysosporium have the ability to degrade an extremely diverse range of persistent or
toxic environmental pollutants, such as Acromobacter, Alcaligenes, Arthrobacter,
8 Bioremediation of Polluted Soil by Using Plant Growth–Promoting Rhizobacteria
219
The bioremediation of the polluted environment is a complex process which is
influenced by certain factors such as microbial factors including growth until critical
biomass is reached, mutation and horizontal gene transfer, enzyme induction,
enrichment of the capable microbial populations, and production of toxic metabolites; environmental factors include depletion of preferential substrates, lack of
nutrients, inhibitory environmental conditions viz soil, temperature (Chitara et al.
2017), pH, O 2 and nutrients; substrate factor includes too low concentration of
contaminants, chemical structure of contaminants, toxicity of contaminants, and
solubility of contaminants; biological aerobic vs anaerobic process factor includes
oxidation/reduction potential, availability of e-accepters, and microbial population
present in the site; growth substrate vs co-metabolism factor includes type of
contaminants, concentration, alternate carbon source present, and microbial interaction (competition, succession, and predation); physico-chemical bioavailability of
pollutants include equilibrium sorption, irreversible sorption, and incorporation into
humic matters, and some of the mass transfer limitations are O 2 diffusion and
solubility, diffusion of nutrients, and solubility/miscibility in/with water (Boopathy
2000). The microorganisms are cosmopolitan in nature which can be isolated from
everywhere such as at subzero temperatures, extreme heat, desert conditions, in
water, with an excess of oxygen, and in anaerobic conditions, with the presence of
hazardous compounds or on any waste stream (Boopathy 2000). The microbes
utilize the energy source and carbon source and other biological systems. These
microbes can be used to remediate environmental hazards. Joshi (2018) divided the
microbes into two groups viz. aerobic and anaerobic groups as follows:
8.9.1 Aerobic
This group includes those microbes which exist in the presence of oxygen (Rayu
et al. 2012), e.g., Pseudomonas, Alcaligenes, Sphingomonas, Rhodococcus, and
Mycobacterium. These bacteria are helpful in bioremediation of polluted soil and
are reported to degrade pesticide and hydrocarbon both as well as alkenes
compounds.
8.9.2 Anaerobic
This group includes those microbes which exist in the absence of oxygen (Rayu et al.
2012); for example ligninolytic fungi such as the white-rot fungus Phanaerochaete
chrysosporium have the ability to degrade an extremely diverse range of persistent or
toxic environmental pollutants, such as Acromobacter, Alcaligenes, Arthrobacter,
8 Bioremediation of Polluted Soil by Using Plant Growth–Promoting Rhizobacteria
219