Green Chemistry and Biosurfactant Research - Biosurfactants: Research Trends and Applications - page 22

and corn steep liquor as substrates for anionic glycolipid production by
Candida sphaerica , while the biosynthesis of glycolipids by P. aeruginosa
was obtained using cashew apple juice as substrate (Rocha et al., 2007) and
vegetable oil refinery wastes (Raza et al., 2007), thus complying with the
first principle of green chemistry, that is, to Prevent Waste.

• A BS from P. aeruginosa was compared with a synthetic surfactant (Marlon

A-350) widely used in industry in terms of toxicity and mutagenic proper-
ties. Both assays indicated the higher toxicity and mutagenic effect of the
chemical-derived surfactant, whereas BS was considered slightly to non-
toxic and nonmutagenic (Flasz et al., 1998). The comparison of acute and
chronic toxicity of three synthetic surfactants (Corexit, 9500, Triton X-100,
and PSE-61) and three microbial-derived surfactants (rhamnolipid, emul-
san, and biological cleanser PES-51) commonly used in oil spill remedia-
tion revealed that PES-61 (synthetic surfactant) and emulsan (BS) were the
least toxic whereas Triton X-100 (synthetic) was the most toxic (Edwards
et al., 2003), complying with principle 4 of green chemistry, that is, Design
for Safer Chemicals.

• Unlike synthetic surfactants, microbial-produced compounds are easily

degraded (Mohan et al., 2006) and particularly suited for environmental appli-
cations such as bioremediation (Deleu and Paquot, 2004; Mulligan, 2005).
The increasing environmental concern among consumers and the regula-
tory rules imposed by governments forced industry to search for alternative
products such as BSs; thus, they are biodegradable fulfilling Principle 11 of
the 12 principles of green chemistry given in the earlier pages of this chapter.

CONCLUSIONS
Green chemistry is not a new branch of science. It is a new philosophical approach
that through application and extension of the principles of green chemistry can
contribute to sustainable development. Great efforts are still undertaken to design
an ideal process that starts from nonpolluting initial materials, leads to no sec-
ondary products, and requires no solvents to carry out the chemical conversion
or to isolate and purify the product. BS research is a promising approach toward
this goal. The BSs seem to enhance the solubilization and emulsification of the
contaminants. Due to their biodegradability and low toxicity, BSs such as rhamno-
lipids are very promising for use in remediation technologies. In addition, there is
the potential for in situ production, a distinct advantage over synthetic surfactants.
This needs to be studied further. Further research regarding prediction of their
behavior in the fate and transport of contaminants will be required. More investi-
gation into the solubilization mechanism of both hydrocarbons and heavy metals
by BSs is required to enable model predictions for transport and remediation. New
applications for the BSs regarding nanoparticles are developing. Future research
should focus on the stabilization of the nanoparticles by BSs before addition dur-
ing remediation procedures.