thus the complete or partial mineralization of environmental organic contaminants,
largely by microorganisms. Thus, biodegradation represents a natural mechanism
through which contaminating petroleum hydrocarbon contaminants can be removed
from the environment.
Petroleum hydrocarbons vary in their susceptibility to microbial degradation,
generally being the highest for low molecular weight alkanes, lowest for polycyclic
aromatics (PAH), and asphaltenes, the latter being the least susceptible (Das and
Chandran 2011; Ite and Ibok 2019). However, this may be contradicted, depending
on the strain of microbe present in the environment and other factors that affect
degradation (Tables 11.1 and 11.2).
While a vast number of microbes, especially bacteria that have the ability to
degrade petroleum hydrocarbons to varying degrees have been isolated, each species
or strain is capable of utilizing only a specific, and often narrow, range of hydrocarbons. No bacteria that are capable of degrading the entire range of compounds in
crude oil have been reported, although a few notable strains with a wide range have
been isolated (Wang et al. 2011). A recent article reports the use of a thermophilic,
bio-emulsifier-producing strain of Aeribacillus pallidus which demonstrated the
ability to utilize short chain alkanes as well as some aromatics at 60
C (Tao et al.
2019). Fungi on the hand appear to be more versatile and demonstrate a wider
capacity, although they have a slower turnover compared to bacteria.
The renewed interest in green technology to manage petroleum pollution continues to drive the search for newer, more efficient, and more versatile microbes with
a capacity to overcome the main challenges of bioremediation of petroleum hydrocarbons (PH), obtaining high efficiency of degradation and complete degradation of
all the components of crude oil.
The tables below summarize a selection of microbes investigated, either singly or
as consortia, for the degradation of petroleum hydrocarbons, specifying the substrate
used and the efficiencies obtained for biodegradation.
11.5 Uptake of Hydrocarbons by Microbes
11.5.1 Chemotaxis
Some bacteria such as Pseudomonas have been shown to use chemotaxis to reach the
hydrocarbon molecules, and expression of related proteins has been reported to be
upregulated when cultured in crude oil at 500 mg/L. However, under very high
concentration of crude oil (20,000 mg/L), it was found that chemotaxis was
inhibited, while the secretion of an emulsifier was increased (Wang et al. 2019b).
11 Microbial Bioremediation of Petroleum Hydrocarbons
269
largely by microorganisms. Thus, biodegradation represents a natural mechanism
through which contaminating petroleum hydrocarbon contaminants can be removed
from the environment.
Petroleum hydrocarbons vary in their susceptibility to microbial degradation,
generally being the highest for low molecular weight alkanes, lowest for polycyclic
aromatics (PAH), and asphaltenes, the latter being the least susceptible (Das and
Chandran 2011; Ite and Ibok 2019). However, this may be contradicted, depending
on the strain of microbe present in the environment and other factors that affect
degradation (Tables 11.1 and 11.2).
While a vast number of microbes, especially bacteria that have the ability to
degrade petroleum hydrocarbons to varying degrees have been isolated, each species
or strain is capable of utilizing only a specific, and often narrow, range of hydrocarbons. No bacteria that are capable of degrading the entire range of compounds in
crude oil have been reported, although a few notable strains with a wide range have
been isolated (Wang et al. 2011). A recent article reports the use of a thermophilic,
bio-emulsifier-producing strain of Aeribacillus pallidus which demonstrated the
ability to utilize short chain alkanes as well as some aromatics at 60
C (Tao et al.
2019). Fungi on the hand appear to be more versatile and demonstrate a wider
capacity, although they have a slower turnover compared to bacteria.
The renewed interest in green technology to manage petroleum pollution continues to drive the search for newer, more efficient, and more versatile microbes with
a capacity to overcome the main challenges of bioremediation of petroleum hydrocarbons (PH), obtaining high efficiency of degradation and complete degradation of
all the components of crude oil.
The tables below summarize a selection of microbes investigated, either singly or
as consortia, for the degradation of petroleum hydrocarbons, specifying the substrate
used and the efficiencies obtained for biodegradation.
11.5 Uptake of Hydrocarbons by Microbes
11.5.1 Chemotaxis
Some bacteria such as Pseudomonas have been shown to use chemotaxis to reach the
hydrocarbon molecules, and expression of related proteins has been reported to be
upregulated when cultured in crude oil at 500 mg/L. However, under very high
concentration of crude oil (20,000 mg/L), it was found that chemotaxis was
inhibited, while the secretion of an emulsifier was increased (Wang et al. 2019b).
11 Microbial Bioremediation of Petroleum Hydrocarbons
269