Biosurfactants and Bioemulsifiers from Marine Sources - Biosurfactants: Research Trends and Applications - page 131

mannopyranosyl(1α-3)-6-acylman-nopyranosyl( 1 α-1)-3-acylglycerol on arti-
ficial seawater supplemented with glucose, yeast extract, peptone, and nitrogen/
phosphate sources (Palme et al., 2010). The third marine bacterium, B. pumilus strain
AAS3 isolated from the Mediterranean sponge Acanthella acuta and synthesized
a diglucosyl-glycerolipid (GGL 11), 1,2-o-diacyl-3-[β-glucopyranosyl-(1-6)-β-
glucopyranosyl)]glycerol, when grown on artificial medium provided with glucose,
yeast extract, peptone, and nitrogen/phosphate sources (Ramm et al., 2004).
Extracellular polysaccharide-lipids (ESL) and polysaccharides (PS) : ESLs and PSs
are another class of BSs produced by marine microbes, and reports on ESLs and
PSs contribute 10% of total publications on marine BSs (Figure 5.2). Acinetobacter
calcoaceticus RAG-1 strain (formally known as Arthrobacter RAG-1) was isolated
from tar balls collected in beach soil (Rosenberg et al., 1979). RAG-1 strain produced
an emulsifier called emulsan, an extracellular polyanionic amphipathic heteropolysac-
charide. Its amphipathic and polymeric characteristics provide it with emulsifying as
well as stabilizing activity of oil/water systems. The bioemulsifier exhibits specificity
toward its hydrocarbon emulsifiable substrates. It tends to concentrate at the oil/water
interface of the hydrocarbon droplets preventing their coalescence and allowing the
formation of concentrated emulsanosols, which were found to be useful in enhancing
oil degradation, binding heavy metal cations or constituting a low-viscosity stable
oil-in-water emulsion suitable for oil pipeline transportation or direct combustion.
Emulsan was also found to protect its producing cells against the toxic cationic deter-
gent cetyltrimethylammonium bromide (Shabtai and Gutnick, 1986).
Another marine bacterium Alcaligenes sp. PHY 9 L-86 was isolated from hydro-
carbon-polluted sea-surface waters that produced surface active exopolysaccharides
(extracellular carbohydrates) and lipids on a medium containing 0.1% tetradecane.
Chemical analysis revealed the composition of the extracellular lipids as phospholip-
ids, free fatty acids, triglycerides, monoglycerides, esters, and free fatty acids (73%) as
the major constituent (Goutx et al., 1987). A PS BS-producing P. putida ML2 strain
was also isolated from hydrocarbon-polluted sediment collected at the Montevideo
bay (Uruguay). Chemical composition of the PS BS revealed its sugar composition as
rhamnose, glucose, and glucosamine in a 3:2:1 molar ratio with a molecular weight
of 10-80 kDa. Another PS surfactant-producing marine Planococcus strain called
P. maitriensis Anita I was isolated from coastal area of Gujarat, India (Kumar et al.,
2007). The extracellular polymeric substance produced had a chemical composition
of carbohydrate (12.06%), protein (24.44%), uronic acid (11%), and sulfate (3.03%) and
effectively emulsified xylene and formed stable emulsions with jatropha, paraffin, and
silicone oils. Its cell-free supernatant reduced the surface tension of water from 72 to
46.07 mN/m.
Glycolipopeptides, Glycolipoproteins, and Glycoproteins (GLPs): Glycolipopeptide
and glycolipoprotein BSs are made of sugar-lipid-peptides or amino acids. GLPs
are the third most studied surfactants among marine BSs, and reports on GLPs con-
tribute 19% of total publications (Figure 5.3). Corynebacterium kutscheri, a marine
bacterium isolated by Thavasi et al. (2007) from Tuticorin harbor, India, produced
a glycolipopeptide BS. The BS was composed of carbohydrate (40%), lipid (27%),
and protein (29%) and was able to emulsify waste motor lubricant oil, crude oil,