4.11 Alkaliphiles in Bioconstruction
Microorganisms contribute to the construction industries in various ways through a
discipline known as construction biotechnology. One of the growing trends is the
consideration of calcite precipitating alkaliphiles in repairing existing concrete
cracks, surface biodeposition (biocoating) and making self-healing concrete (see
[252]). Since concrete is very alkaline in nature, the use of alkaliphiles is ideal, and
several of them have been studied for these applications. The same principle of
microbial-induced carbonate precipitation has been used in the construction industries for several years as a mineral-plugging material, a technique suitable for
enhanced oil recovery, cementing unconsolidated ground, restricting the flow of
contaminants to aquifer, and plugging pores and channels in soil or fractured rock to
limit hydraulic conductivity [253–255]. Moreover, it is used in increasing soil
particle cohesion to reduce erosion and dust emission [256, 257] as well as to bind
sand grains together to mitigate desert expansion. One of the most important
parameters for carbonate precipitation is pH. The higher the pH, the better the
precipitation and the more stable are the crystals. Thus, alkaliphiles with calcite
precipitation properties could be attractive alternatives for these applications.
In addition to biomineralization processes, microbes can be used in construction
activities through their organic products. An important product in this line could be
the exopolysaccharides such as xanthan, curdlan, succinoglucan, and welan which
are used in preparations including wall plasters, concrete and dry-mix mortars,
injection grouts, and self-leveling underlayers [258]. These admixtures are used to
improve the water retention property, viscosity, set retarding, and flowability of the
preparations [259]. As aforementioned, some alkaliphilic strains are known to be
producing high amount of exopolysaccharides, and, hence, alkaliphiles potentially
can be interesting sources of exopolysaccharides for the construction industry.
Alkaliphiles can be applied in construction sector in various ways, and some of
these applications are shown in Fig. 7.
4.12 Alkaliphiles in Mining and Oil Drilling
There is not much published work in the use of alkaliphiles in mining and oil
drilling. However, the limited studies done so far show the potential of some
alkaliphiles in oil extraction and mining. For instance, the alkaliphilic strain
Alkaliphilus metalliredigens is known to grow at extremely high pH using
chelator-bound metal ions such as Co(III)-EDTA, Fe(III)-citrate, Fe(III)-EDTA,
and Cr(VI) as electron acceptors. Such kind of metal-reducing alkaliphilic bacterium
may be useful for bioleaching of metals at alkaline and anaerobic conditions
[260]. Indeed, A. metalliredigens-driven metal reduction and mineral formation
has been demonstrated by [261]. Another alkaliphile that reduces Cr(VI) at alkaline
condition is a strain of Amphibacillus sp. [262].
32
G. Mamo and B. Mattiasson
Microorganisms contribute to the construction industries in various ways through a
discipline known as construction biotechnology. One of the growing trends is the
consideration of calcite precipitating alkaliphiles in repairing existing concrete
cracks, surface biodeposition (biocoating) and making self-healing concrete (see
[252]). Since concrete is very alkaline in nature, the use of alkaliphiles is ideal, and
several of them have been studied for these applications. The same principle of
microbial-induced carbonate precipitation has been used in the construction industries for several years as a mineral-plugging material, a technique suitable for
enhanced oil recovery, cementing unconsolidated ground, restricting the flow of
contaminants to aquifer, and plugging pores and channels in soil or fractured rock to
limit hydraulic conductivity [253–255]. Moreover, it is used in increasing soil
particle cohesion to reduce erosion and dust emission [256, 257] as well as to bind
sand grains together to mitigate desert expansion. One of the most important
parameters for carbonate precipitation is pH. The higher the pH, the better the
precipitation and the more stable are the crystals. Thus, alkaliphiles with calcite
precipitation properties could be attractive alternatives for these applications.
In addition to biomineralization processes, microbes can be used in construction
activities through their organic products. An important product in this line could be
the exopolysaccharides such as xanthan, curdlan, succinoglucan, and welan which
are used in preparations including wall plasters, concrete and dry-mix mortars,
injection grouts, and self-leveling underlayers [258]. These admixtures are used to
improve the water retention property, viscosity, set retarding, and flowability of the
preparations [259]. As aforementioned, some alkaliphilic strains are known to be
producing high amount of exopolysaccharides, and, hence, alkaliphiles potentially
can be interesting sources of exopolysaccharides for the construction industry.
Alkaliphiles can be applied in construction sector in various ways, and some of
these applications are shown in Fig. 7.
4.12 Alkaliphiles in Mining and Oil Drilling
There is not much published work in the use of alkaliphiles in mining and oil
drilling. However, the limited studies done so far show the potential of some
alkaliphiles in oil extraction and mining. For instance, the alkaliphilic strain
Alkaliphilus metalliredigens is known to grow at extremely high pH using
chelator-bound metal ions such as Co(III)-EDTA, Fe(III)-citrate, Fe(III)-EDTA,
and Cr(VI) as electron acceptors. Such kind of metal-reducing alkaliphilic bacterium
may be useful for bioleaching of metals at alkaline and anaerobic conditions
[260]. Indeed, A. metalliredigens-driven metal reduction and mineral formation
has been demonstrated by [261]. Another alkaliphile that reduces Cr(VI) at alkaline
condition is a strain of Amphibacillus sp. [262].
32
G. Mamo and B. Mattiasson