11.6.1 Bioremediation

Bioremediation is a novel technology accomplished by a complex chain of biologically

mediated transformation. It is a promising and inventive system that uses microorgan­

isms to decontaminate pollutants. In another word, bioremediation is defined as a process

that uses microorganisms for clearance or degradation of contaminants and hazardous

substances including toxins, and other organic pollutants under controlled conditions to

an innocuous state [39]. Several advances in bioremediation techniques including ex-situ

and in-situ bioremediation with the microbe and organic pollutants are both present in

the soil. Ex-situ bioremediation is considered a faster method based on: the cost of

treatment, type of pollutant, and geology of the polluted site. The main goal of this

technique is to effectively restore polluted environments. Several techniques include in-

situ remediation such as bioslurping, biosparging, bioaugmentation, etc. however, in ex-

situ the most employed techniques are biopile, windrows, composting, and bioreactors

[40]. Therefore, it is highly involved in the degradation, eradication, immobilization, or

detoxification of various chemicals and hazardous physical materials from the environ­

ment through microorganisms. Today, bioremediation is a permanent solution that can

reduce or degrade pollutants and control dangerous substances in subsurface environ­

ments. Recently, a new strategy for the bioremediation of toxic metal contaminants has

been used in agricultural soils, industrial environments, and waters reservoir by using the

microorganism to decompose substances such as hydrocarbons, petroleum, heavy metals,

pesticides, among others. Generally, the pollutants can be remediated through three basic

levels. First, through natural attenuation, at which pollutants are reduced by native mi­

croorganisms. Second, biostimulation is employed where nutrients and oxygen are ap­

plied to accelerate biodegradation. The third level is during bioaugmentation, at which

organisms are added to improve the efficiency when compared to native microorganisms

to reduce the contaminants. The efficiency of bioremediation to reduce environmental

pollutants is strongly related to the appropriate species employed to degrade the che­

micals. In that sense, many microbes have the potential for environmental restoration by

removing metals contaminated water. For example, the Geobacter and S. oneidensis MR-1

play a role in the bioremediation processes by potentially degrading a diverse number of

contaminants including Cr and U [41,42]. The capacity to reduce radionuclides like U(VI)

by S. oneidensis MR-1 strain is correlated with the presence of c-type cytochromes [26].

Yet, the reduced solubility of U(VI) in sedimentary environments imposes a challenge

that requires novel strategies for bioremediation to properly eliminate this environmental

pollutant. The capacity of these microorganisms to degrade many other compounds in­

cluding radionuclides elements, minerals substances like nitrite, sulfate, chromium, dye

solution contaminated wastewaters, and petroleum-contaminated by S. oneidensis MR-1,

are described in various studies [43,44].

11.6.2 Bioelectricity and Bioenergy Production

The interaction between the microorganisms and insoluble electron donors or acceptors is

an emerging field within applied microbiology. The term electromicrobiology is a research

area of science that studies the mechanism of microbial electron exchange that has

contributed to developing a branch of bioelectronics [44,45]. A considerable amount of

microorganisms have metallic-like properties that provide them with electronic char­

acteristics. There are three types of microbial EET mechanisms at the anode of microbial

fuel cells (MFCs), including direct/indirect transfers and through conductive nanowires,

which are provided in Figure 11.6 [44].

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Bioelectronics