3.11 Biotechnological Applications of Manganese Oxidation
Manganese, a comparatively less toxic element, can become toxic to domestic and
aquatic lives when its concentration exceeds beyond the EPA permissible levels
(0.05 mg L
À1 ). During summer, it is observed that Mn oxides undergo reduction
when the oxygen level drops in public and private wells, municipal water supplies,
etc. The solubilized Mn is quite stable in the presence of oxygen and therefore can
become a health risk for public who consumes the drinking water. The Mnoxidizing bacterial residents of the Mn
2+ -rich environments can oxidize Mn
2+ and
reduce its solubility and thereby provide protective mechanism against toxic levels
of soluble Mn (Bromfield 1978). An application of Mn oxidizers or their products to
such habitats offer chemical/biological solution to the problem on a seasonal/
permanent basis (Czekalla et al. 1985). Mn oxides are also excellent electron
acceptors for anaerobic respiration (Nealson et al. 1989). The application of Mnoxidizing bacteria and Mn in sedimentary environments can stimulate respiratory
carbon mineralization and could offer a natural system of “Pumping” (via precipitation and sedimentation of Mn oxides) electron-acceptor equivalents into an
anaerobic environment (Nealson et al. 1989). It is observed that Mn oxides are
potent chelators of several other trace metals, their application has proved to be
efficient in the removal of radium from water supplies (Moore and Reid 1973), in
retaining heavy metals like Co, Ni, Zn, and others in soil, polymerization of organic
compounds, participation in humus formation by oxidation of phenols and quinines
(Vodyanitskii 2009).
The removal of Mn
2+ is conventionally achieved by inorganic oxidation such as
chlorination or permanganate oxidation, followed by sand filtration (Miyata et al.
2007). In 1986, Ghiorse proposed the exploitation of Mn-precipitating microorganisms for industrial metal recovery processes. The use of Mn-oxidizing bacteria in treating effluents can minimize the addition of chemical reagents and
unwanted by-product formation. The increase in filtration rate and longer runs
due to less clogging, savings on wash water, and rapid return to equilibrium
following a backwash sequence reduce the operational cost in treatment and maintenance of sludge in biological effluent treatment (Mouchet 1992; Katsoyiannis and
Zouboulis 2004; Stembal et al. 2005). The biological processes take advantage of
active and passive process in treatment by a variety of mechanisms like adsorption,
accumulation, precipitation, and oxidation. The drawback of using bacteria for
treating effluent biotechnologically is the slow rate of Mn oxidation. As an early
solution to the problem, Stuetz et al. (1996) proposed the usage of combined
algal–bacterial Mn oxidation and optimization of bioreactor parameters for treating
metal effluents effectively. When using Mn oxide (scavengers of the environment)
for treatment of any effluents with unknown composition, precaution needs to be
taken as it is known that sometimes interaction of Mn oxide with other elements can
result in phase transformations [Se(IV) to Se(VI), Cr(III) to Cr(VI), and As(III) to
As(V)], contributing to increase/decrease in metal toxicity (Vodyanitskii 2009; He
et al. 2010).
3 Manganese Oxidation by Bacteria: Biogeochemical Aspects
65
Manganese, a comparatively less toxic element, can become toxic to domestic and
aquatic lives when its concentration exceeds beyond the EPA permissible levels
(0.05 mg L
À1 ). During summer, it is observed that Mn oxides undergo reduction
when the oxygen level drops in public and private wells, municipal water supplies,
etc. The solubilized Mn is quite stable in the presence of oxygen and therefore can
become a health risk for public who consumes the drinking water. The Mnoxidizing bacterial residents of the Mn
2+ -rich environments can oxidize Mn
2+ and
reduce its solubility and thereby provide protective mechanism against toxic levels
of soluble Mn (Bromfield 1978). An application of Mn oxidizers or their products to
such habitats offer chemical/biological solution to the problem on a seasonal/
permanent basis (Czekalla et al. 1985). Mn oxides are also excellent electron
acceptors for anaerobic respiration (Nealson et al. 1989). The application of Mnoxidizing bacteria and Mn in sedimentary environments can stimulate respiratory
carbon mineralization and could offer a natural system of “Pumping” (via precipitation and sedimentation of Mn oxides) electron-acceptor equivalents into an
anaerobic environment (Nealson et al. 1989). It is observed that Mn oxides are
potent chelators of several other trace metals, their application has proved to be
efficient in the removal of radium from water supplies (Moore and Reid 1973), in
retaining heavy metals like Co, Ni, Zn, and others in soil, polymerization of organic
compounds, participation in humus formation by oxidation of phenols and quinines
(Vodyanitskii 2009).
The removal of Mn
2+ is conventionally achieved by inorganic oxidation such as
chlorination or permanganate oxidation, followed by sand filtration (Miyata et al.
2007). In 1986, Ghiorse proposed the exploitation of Mn-precipitating microorganisms for industrial metal recovery processes. The use of Mn-oxidizing bacteria in treating effluents can minimize the addition of chemical reagents and
unwanted by-product formation. The increase in filtration rate and longer runs
due to less clogging, savings on wash water, and rapid return to equilibrium
following a backwash sequence reduce the operational cost in treatment and maintenance of sludge in biological effluent treatment (Mouchet 1992; Katsoyiannis and
Zouboulis 2004; Stembal et al. 2005). The biological processes take advantage of
active and passive process in treatment by a variety of mechanisms like adsorption,
accumulation, precipitation, and oxidation. The drawback of using bacteria for
treating effluent biotechnologically is the slow rate of Mn oxidation. As an early
solution to the problem, Stuetz et al. (1996) proposed the usage of combined
algal–bacterial Mn oxidation and optimization of bioreactor parameters for treating
metal effluents effectively. When using Mn oxide (scavengers of the environment)
for treatment of any effluents with unknown composition, precaution needs to be
taken as it is known that sometimes interaction of Mn oxide with other elements can
result in phase transformations [Se(IV) to Se(VI), Cr(III) to Cr(VI), and As(III) to
As(V)], contributing to increase/decrease in metal toxicity (Vodyanitskii 2009; He
et al. 2010).
3 Manganese Oxidation by Bacteria: Biogeochemical Aspects
65