EFFECT OF ADDITION OF RHAMNOLIPID BIOSURFACTANTS OR RHAMNOLIPID-PRODUCING PSEUDOMONAS-AERUGINOSA ON PHENANTHRENE MINERALIZATION IN SOIL SLURRIES

The effect of Pseudomonas aeruginosa UG2 biosurfactants or UG2 inocula on phenanthrene mineralization in uninoculated nonsterile soil slurri es and slurries inoculated with the phenanthrene-mineralizing Pseudomo nas sp. UG14r was investigated. In sandy loam and silt loam slurries a mended with phenanthrene, inoculation with UG14r alone or in co-cultur e with UG2Lr reduced the lag period before onset of phenanthrene miner alization by 1 week. The total amount mineralized after 5 weeks was lo wer st not significantly different from the uninoculated control slurr ies. Inoculation with P. aeruginosa UG2Lr alone did not improve phenan threne mineralization. In creosote-contaminated soil slurries, no lag period in phenanthrene mineralization was observed in any treatment. A fter 4 weeks, the greatest extent of mineralization was observed in cr eosote-contaminated soil slurries inoculated with the UG14r-UG2Lr co-c ulture and UG14r alone. In sandy loam and silt loam soil slurries inoc ulated with Pseudomonas sp. UG14r, addition of UG2 rhamnolipid biosurf actants (100 to 400 mg rhamnose equivalents (RE) . l(-1) slurry) inhib ited phenanthrene mineralization by 10 to 15%. Mineralization was also inhibited in uninoculated sandy loam slurries. In creosote-contaminat ed soil slurries inoculated with Pseudomonas sp. UG14r, biosurfactants at 250 mg RE . l(-1) slurry enhanced mineralization whereas 400 mg RE . l(-1) had no effect, compared to unamended slurries. In uninoculate d creosote-contaminated soil slurries, UG2 biosurfactants at 250 and 4 00 mg RE . l(-1) slurry enhanced mineralization, compared to unamended slurries.