FEMS Microbiology Ecology 17 (1995) 15-26 Effect of addition of rhamnolipid biosurfactants or rhamnolipid-producing zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA Pseudomonas aeruginosa on phenanthrene mineralization in soil slurries Miguel A. Providenti, Cecily A. Flemming, Hung Lee *, Jack T. Trevors * zyxwvutsrqponm Department zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA of Environmental Biology, University of Guelph, Guelph, Ontario Canada, NlG 2W1 Received 24 October 1994; revised 10 February 1995; accepted 12 February 1995 zyxwvutsrqponmlkjihgfedcbaZ Abstract The effect of Pseudomonas aeruginosa UG2 biosurfactants or UG2 inocula on phenanthrene mineralization in uninoculated nonsterile soil slurries and slurries inoculated with the phenanthrene-mineralizing Pseudomonas sp. UG14r was investigated. In sandy loam and silt loam slurries amended with phenanthrene, inoculation with UG14r alone or in co-culture with UG2Lr reduced the lag period before onset of phenanthrene mineralization by 1 week. The total amount mineralized after 5 weeks was lower or not significantly different from the uninoculated control slurries. Inoculation with P. aeruginosa UG2Lr alone did not improve phenanthrene mineralization. In creosote-contaminated soil slurries, no lag period in phenanthrene mineralization was observed in any treatment. After 4 weeks, the greatest extent of mineralization was observed in creosote-contaminated soil slurries inoculated with the UG14r-UG2Lr co-culture and UG14r alone. In sandy loam and silt loam soil slurries inoculated with Pseudomonas sp. UG14r, addition of UG2 rhamnolipid biosurfactants (100 to 400 mg rhamnose equivalents zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA (RE) I-’ slurry) inhibited phenanthrene mineralization by 10 to 15%. Mineralization was also inhibited in uninoculated sandy loam slurries. In creosote-contaminated soil slurries inoculated with Pseudomonas sp. UG14r, biosurfactants at 250 mg RE . 1-l slurry enhanced mineralization whereas 400 mg zyxwvutsrqponmlkjihgfedcbaZYXW RE . 1-l had no effect, compared to unamended slurries. In uninoculated creosote-contaminated soil slurries, UG2 biosurfactants at 250 and 400 mg RE I- ’ slurry enhanced mineralization, compared to unamended slurries. Keywords: Bacteria; Bioremediation; Biosurfactant; Creosote-contaminated; Phenanthrene; Soil; Survival 1. Introduction Biological remediation of hydrocarbon-con- taminated soil is an alternative to physical or chemi- cal methods [l]. However, numerous factors limit * Corresponding author. Tel: (519) 824-4120, Ext. 3828; Fax: (519) 837-0442; E-mail: hlee@uoguelph.ca or jtrevors@ uoguelph.ca biodegradation of pollutants in the environment [2]. One factor is the limited availability of contaminants to microorganisms. Contaminants may be unavail- able because of their hydrophobic nature and sorp- tion to soil. Treating soil with surfactants can in- crease contaminant availability to degrading mi- croorganisms. Several studies have shown that treat- ment with synthetic surfactants can improve contam- inant removal from soil in columns [3-61 and in Federation of European Microbiological Societies. SD! 0168-6496(95)00007-O Downloaded from https://academic.oup.com/femsec/article/17/1/15/558667 by guest on 29 June 2022