Sa. Churchill et al., BIODEGRADATION RATE ENHANCEMENT OF HYDROCARBONS BY AN OLEOPHILIC FERTILIZER AND A RHAMNOLIPID BIOSURFACTANT, Journal of environmental quality, 24(1), 1995, pp. 19-28
The oleophilic fertilizer Inipol EAP 22 and a microbial biosurfactant
(rhamnolipid) were investigated for their ability to increase the rate
of biodegradation of aliphatic and aromatic hydrocarbons by pure bact
erial cultures. Both Inipol EAP 22 and rhamnolipid were found to lower
the surface tension of a phosphate buffered solution to 32 mN m(-1).
Each surfactant dramatically increased the apparent aqueous solubility
of solid 2-methylnaphthalene, and were capable of emulsifying liquid
hydrocarbons. Biodegradation experiments were carried out with the TOL
plasmid-containing strain, Pseudomonas putida (ATCC30015); the OCT pl
asmid-containing strain, P. oleovorans (ATCC29347); and an unknown nap
hthalene-degrading strain (ATCC15075). Cells were grown under conditio
ns where biodegradative enzymes were induced before their utilization.
Model studies were conducted to investigate the ability of Inipol EAP
22 and rhamnolipid to enhance the rate of transport and uptake of hyd
rocarbons into bacterial cells, and to assess the impact that increasi
ng the apparent aqueous solubility of hydrocarbons has on their rate o
f biodegradation. The extent of rate enhancement of compound mineraliz
ation resulting from surfactant addition was significantly greater for
the sparingly soluble alkanes, hexadecane and octadecane, than for th
e more soluble aromatics, toluene and 2-methylnaphthalene. The results
suggest that increasing the bioavailability of hydrocarbons to bacter
ia may be a useful method to accelerate the rate of biodegradation at
contaminated sites. Lastly, the data supports the hypothesis that surf
ace-active components present in the oleophilic fertilizer formulation
, Inipol EAP 22, may have significantly contributed to the positive re
sults reported in tests of remedial agent impact on bioremediation, wh
ich was used as a supplemental cleanup technology on Exxon Valdez crud
e oil contaminated Alaskan beaches.