Green Chemistry and Biosurfactant Research - Biosurfactants: Research Trends and Applications - page 12

Only recently, a small fieldscale MEOR experiment has provided for the first-time
data of in situ metabolism and activities. Molecular techniques combined with
traditional methods showed that Bacillus strains injected into oil wells main-
tained activity, consuming the glucose and nutrients supplied and releasing CO 2
and fermentation products including a lipopeptide BS leading to an increased
production estimated as one barrel of oil/day over 7 weeks after the treatment
(Perfumo et al., 2010).
Bioremediation involves the acceleration of natural biodegradative processes in
contaminated environments by improving the availability of materials (e.g., nutri-
ents and oxygen), conditions (e.g., pH and moisture content), and prevailing micro-
organisms. Thus, bioremediation usually consists of the application of nitrogenous
and phosphorous fertilizers, adjusting the pH and water content, if necessary, sup-
plying air, and often adding bacteria. The addition of emulsifiers is advantageous
when bacterial growth is slow (e.g., at cold temperatures or in the presence of high
concentrations of pollutants) or when the pollutants consist of compounds that are
difficult to degrade, such as polycyclic aromatic hydrocarbons. Bioemulsifiers can
be applied as an additive to stimulate the bioremediation process; however, with
advanced genetic technologies, it is expected that the increase in bioemulsifier con-
centration during bioremediation would be achieved by the addition of bacteria that
overproduce bioemulsifiers.
e nhanCeD B ioremeDiation of o rGaniC C ontamination
The enhanced bioremediation of organic contaminants by BSs is currently being
studied. The ability of the rhamnolipid to remove styrene from contaminated soil
was evaluated by Guo and Mulligan (2006). It was shown that it was feasible to
use rhamnolipid as a washing agent to remove styrene. The results show that more
than 70% of removal could be achieved for 32,750 mg/kg of styrene after 1 day
and 88.7% removal after 5 days, while a 90% removal was obtained for 16,340
mg/kg of styrene after 1 day. After removal from the soil by rhamnolipid, more than
70% of the styrene could be biodegraded by an anaerobic biomass, in a combined
soil flushing, and leachate treatment process. As marine oil spills can pose great
threats and cause extensive damage to the marine and coastal ecosystems, the aim
of the study by Vasefy and Mulligan (2008) was to evaluate the effectiveness of
two commercial biological products, ASAP™ and Degreaser™, and a rhamnolipid
BS (JBR 425™) on the biodegradation of weathered light crude oil, heavy crude
oil, and diesel fuel spilled on saline water following the USEPA's biological effec-
tiveness test method. The two evaluated products contain bacterial consortia and
nutrients and were used as supplementary additives to enhance the biodegradation
rate and the extent of hydrocarbon compounds. Chemical analysis was conducted by
using gas chromatography/flame ionization detection to determine the fate of weath-
ered oils in saline water over a 28-day experiment. Microbiological analysis was
also performed to determine and monitor the viability of the microbial growth by
addition of different rhamnolipid and commercial product concentrations to the oil
samples. Degradation rates of oil types for most of the treatments were in the order
of diesel fuel > light crude oil > heavy crude oil, and generally removal percentage