Biomedical Engineering Reference
In-Depth Information
the membrane that was used for separating rhamnolipids was 50,000 Daltons, and
it was able to retain 92% of the rhamnolipids. They also noted that these ultrafil-
tration membranes can be incorporated with the process of continuous biosurfac-
tant production.
OPTIMIZATION OF THE RHAMNOLIPID BIOSYNTHESIS
Researchers are working intensively to determine the genetic details underlying the
rhamnolipid production by
P. aeruginosa
. Despite the recent advances in the tech-
nology, researchers are in the first steps of solving the unknowns, and there are many
questions to be solved in this field.
According to Abdel-Mawgoud et al. (2011), for rhamnolipids, the synthesis of
the lipid part takes place through the pathway of fatty acid synthesis from carbon
units; therefore, the type and the structure of the lipid part of the rhamnolipid do
not depend on the type of carbon source being used. Hence, there wouldn't be any
changes in the lipid part following the use of various carbon sources for the cultiva-
tion of bacteria.
The lipid part of the rhamnolipids is synthesized through fatty acid synthesis
type (II), which is a series of disassociated synthesis systems, and each part of the
reactions is controlled by their specific gene. This means that each step of the syn-
thesis and each single reaction are catalyzed by separate proteins that are encoded
by a distinct gene. This type of fatty acid synthesis is observed only in bacteria and
plants. As it have been noted before, to decrease the cost and optimize the production
of the rhamnolipids and enhancing the composition of the product, there have been
many approaches, and in this chapter, a brief summary of some of the main methods
will be discussed.
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isolation
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By increasing the knowledge about the properties of rhamnolipids, new applica-
tions for this valuable material are found. The efficiency of rhamnolipids in many
applications in different areas, from environmental sector (for the bioremediation
of soil and water or fungicide) to cosmetic and food industries, made this material
desirable, and by increasing the demand for it, there is a need to find and isolate
new high-yield rhamnolipid-producing microorganism and the ones that are able to
use low-cost renewable or waste substrates (Mulligan and Gibbs, 2004). Numerous
microorganisms have been found to be able to produce rhamnolipids, and these
rhamnolipid-producing organisms can be found in a variety of environments. They
can be found in both warm and cold climates, they can survive even the toughest
environment such as polluted soils with high salinity, and they evolved to use a
variety of carbon sources.
Rashedi et al. (2006) reported the isolation of 152 bacterial strains from the
contaminated oils in the warm climate of Khuzestan, Iran. They used a hemolysis
method for the initial identification of the biosurfactant-producing microorganisms.
They reported that 55 of isolated strains showed hemolytic activity. Among those 55
strains, only 12 strains could produce biosurfactants with superior surface tension
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