Biosurfactants are highly attractive to be used in industrial products like
cosmetics, pharmaceuticals, agrochemicals, food, medicine, and detergents. Oil
industry is a potential big user of biosurfactants as emulsifiers. Bioremediation
processes could benefit from biosurfactants and even can be produced in situ.
Some biosurfactants have also antibiotic and/or insecticidal properties. The commercial applications and production of biosurfactants have been reviewed by
Fakruddin [26].
Biosurfactants produced and secreted by alkaliphiles are ideal for detergent
formulations which are alkaline. The positive image of eco-friendly products may
justify the higher price, as well. Many reports describe the biosurfactant production
by microbes in moderate pH environments [25–28]. So far, a few alkaliphilic
biosurfactant producers have been isolated from different but rather harsh habitats
such as oil-contaminated saline sites and wastewaters [29–31], alkaline and saline
soda lakes [32–34], hot spring [35], Red Sea water [36], and PAH-contaminated soil
[37]. Their potential to synthesize surfactants was mainly identified by the hemolytic
emulsification activity and reduction in surface tension. Achromobacter
xylosoxidans bacterium from Lonar Lake, India, and archaea Natronolimnobius
innermongolicus WN23 from soda lakes, Egypt, had high degradative potential for
oil and had the emulsification index values 58% and 55%, respectively
[32, 34]. Biosurfactant crude extracts produced by Archaea WN23 and WN26
were stable in a broad pH range of 5–12 and up to 35% (w/v) of NaCl. The change
in the pH did not affect the stability of the emulsion [32].
The influence of media compositions and cultivation conditions on production of
biosurfactants by microorganisms have been extensively studied. Corn powder, an
unconventional carbon source, increased biosurfactant production by alkaliphilic
Klebsiella sp. up to 15.4 g/L against 10.0 g/L with starch [38]. Yield of biosurfactant
of Cronobacter sakazakii in a sucrose-containing medium was 3.15 g/L after 72 h
[31]. In addition to production studies, analysis of the biosurfactants has been
considered. The chemical characteristics of two purified biosurfactants were
analyzed with spectroscopic methods [31, 39]. The compounds were
heteropolysaccharide-protein complexes comprised of glucose, galactose, mannose,
xylose, arabinose, and uronic acid. These compounds were high-molecular-weight
thermally stable biopolymers which exhibited degradation above 260
C. Furthermore, it had low viscosity with pseudoplastic rheological behavior and significant
emulsification activity with oils and hydrocarbons. The isolated biosurfactant of
strain Klebsiella sp. RJ-03 is compatible with detergents and resulted in enhanced oil
removing efficiency from soil and cotton cloths [40].
Maximum biosurfactant production by an Exiguobacterium sp. was found to take
place using coconut oil and brake oil as carbon sources. The best growth was
achieved at pH 10, 50
C, and in the presence of 4% (w/v) of NaCl. It was suggested
that this microbe might be used for remediation of polluted sites in marine environment [33]. Similar results were found with biosurfactant production by alkali-halothermophilic bacteria Virgibacillus salarius. The highest biosurfactant synthesis was
obtained in the presence of 4% (w/v) of NaCl and cultivated at pH 9 and 45–50
C
using frying oil waste as carbon source. The structural analysis confirmed the
170
E. Khalikova et al.
cosmetics, pharmaceuticals, agrochemicals, food, medicine, and detergents. Oil
industry is a potential big user of biosurfactants as emulsifiers. Bioremediation
processes could benefit from biosurfactants and even can be produced in situ.
Some biosurfactants have also antibiotic and/or insecticidal properties. The commercial applications and production of biosurfactants have been reviewed by
Fakruddin [26].
Biosurfactants produced and secreted by alkaliphiles are ideal for detergent
formulations which are alkaline. The positive image of eco-friendly products may
justify the higher price, as well. Many reports describe the biosurfactant production
by microbes in moderate pH environments [25–28]. So far, a few alkaliphilic
biosurfactant producers have been isolated from different but rather harsh habitats
such as oil-contaminated saline sites and wastewaters [29–31], alkaline and saline
soda lakes [32–34], hot spring [35], Red Sea water [36], and PAH-contaminated soil
[37]. Their potential to synthesize surfactants was mainly identified by the hemolytic
emulsification activity and reduction in surface tension. Achromobacter
xylosoxidans bacterium from Lonar Lake, India, and archaea Natronolimnobius
innermongolicus WN23 from soda lakes, Egypt, had high degradative potential for
oil and had the emulsification index values 58% and 55%, respectively
[32, 34]. Biosurfactant crude extracts produced by Archaea WN23 and WN26
were stable in a broad pH range of 5–12 and up to 35% (w/v) of NaCl. The change
in the pH did not affect the stability of the emulsion [32].
The influence of media compositions and cultivation conditions on production of
biosurfactants by microorganisms have been extensively studied. Corn powder, an
unconventional carbon source, increased biosurfactant production by alkaliphilic
Klebsiella sp. up to 15.4 g/L against 10.0 g/L with starch [38]. Yield of biosurfactant
of Cronobacter sakazakii in a sucrose-containing medium was 3.15 g/L after 72 h
[31]. In addition to production studies, analysis of the biosurfactants has been
considered. The chemical characteristics of two purified biosurfactants were
analyzed with spectroscopic methods [31, 39]. The compounds were
heteropolysaccharide-protein complexes comprised of glucose, galactose, mannose,
xylose, arabinose, and uronic acid. These compounds were high-molecular-weight
thermally stable biopolymers which exhibited degradation above 260
C. Furthermore, it had low viscosity with pseudoplastic rheological behavior and significant
emulsification activity with oils and hydrocarbons. The isolated biosurfactant of
strain Klebsiella sp. RJ-03 is compatible with detergents and resulted in enhanced oil
removing efficiency from soil and cotton cloths [40].
Maximum biosurfactant production by an Exiguobacterium sp. was found to take
place using coconut oil and brake oil as carbon sources. The best growth was
achieved at pH 10, 50
C, and in the presence of 4% (w/v) of NaCl. It was suggested
that this microbe might be used for remediation of polluted sites in marine environment [33]. Similar results were found with biosurfactant production by alkali-halothermophilic bacteria Virgibacillus salarius. The highest biosurfactant synthesis was
obtained in the presence of 4% (w/v) of NaCl and cultivated at pH 9 and 45–50
C
using frying oil waste as carbon source. The structural analysis confirmed the
170
E. Khalikova et al.