Bioprocessing Approaches to Synthesize Bio-based Surfactants and Detergents - Food and Industrial Bioproducts and Bioprocessing - page 253

The biological role of glycolipid biosurfactants appears to be for emulsification of
apolar carbon-energy sources, adhesion of cells to hydrophobic surfaces, energy storage,
and perhaps to provide resistance to high osmotic pressures (Kitamoto et al ., 2009 ).
Recent emphasis has been placed on utilization of low cost, including co-product,
streams as carbon-energy sources for glycolipid biosurfactants production, such as
sophorolipids from glycerine, soy molasses, and whey, and rhamnolipid from used
cooking oil and soapstock and molasses (Nitschke and Costa, 2007; Ashby et al ., 2009 ;
Pinzon et al ., 2009 ).
Glycolipid-type biosurfactants are employed in a variety of applications, due to their
high surface activity, biodegradability, and biocompatibility. Rhamnolipids are useful in
bioremediation and enhanced oil recovery (Pinzon et al ., 2009 ). Sophorolipids are employed
in food encapsulation and, more recently, in dishwasher detergents, and have biomedical
applications (Kitamoto et al ., 2009 ; Ashby et al ., 2009 ). Mannosylerythritol lipids have
several biomedical applications, including the treatment of tumors and as antimicrobial
agents (Arutchelvi et al ., 2008). Mannosylerythritol lipids, sophorolipids, and several other
glycolipid biosurfactants have numerous applications in cosmetics (Lourith and
Kanlayavattanakul, 2009). Trehalose lipids have several environmental and biomedical
applications (Franzetti et al ., 2010 ).
Lipopeptide surfactants, produced primarily by the Pseudomonas and Bacillus bacteria,
typically consist of polypeptides that contain 5-12 D- or L-amino acid residues and a
β -hydroxy fatty acyl group of chain length C 13 -C 18 , typically covalently attached via amide

bond formation at the amino terminus of the polypeptide. Also, many lipopeptides contain
a second linkage, an ester bond between the

-hydroxy group of the fatty acyl moiety and
the carboxylic acid terminus of the polypeptide. Surfactin, an excellent surface-active agent
that can lower the surface tension of water from 72 to 29 mN m -1 at a concentration of only
50

β

M, is depicted in Figure 10.8. Surfactin contains a mixture of molecules similar in
chemical structure to that depicted in the figure with a slight variation in the fatty acyl chain
length. Reviewed elsewhere (McInerney et al ., 2009 ), lipopeptides possess many
applications, including biomedical employment as antibiotics (e.g., surfactin from
B. subtilis ) and inhibitors of blood clotting. Their thermostability and insensitivity to pH and
salinity makes them excellent candidates for oil recovery. Lipopeptides are formed via
fermentation, using carbon and nitrogen starvation conditions. Recent work has involved
utilizing low cost co-product streams as carbon-energy sources, such as molasses (Nitschke
and Costa, 2007 ).
Polymer-type surfactants, typically produced from bacteria or yeast, are primarily
polysaccharides. One example is “emulsan,” an anionic lipoheteropolysaccharide produced
from Acinetobacter venetianus when utilizing lipids or long-chain alkanes as carbon-energy
sources (Mercaldi et al ., 2008). Fatty acyl groups are linked to the polysaccharide backbone
via ester or amide linkages. Its molecular weight is 98 000. Emulsan's main application is
for environmental remediation and oil recovery, with recent investigations showing potential
utility in drug delivery. Alasan, a high molecular weight complex of polysaccharide
containing covalently attached alanine and protein obtained from A. radioresistens , has
similar applications as emulsan (Ahmed et al ., 2009 ). Liposan, obtained from fermentation
of Candida lipopytica using hexadecane as carbon-energy source, contains mainly (83%)
polysaccharide (glucose, galactose, galactosamine, and galacturonic acid units) and the
remainder protein, and has utility as a gelling agent, emulsifier, stabilizer, flocculant,
lubricate, or dispersing agent (Cirigliano and Carman, 1985).

μ