title: Dual partitioning and attachment effects of rhamnolipid on pyrene biodegradation under bioavailability restrictions.
abstract: We investigated the effects of different bioavailability scenarios on the rhamnolipid-enhanced biodegradation of pyrene by the representative polycyclic aromatic hydrocarbon degrader Mycobacterium gilvum VM552. This biosurfactant enhanced biodegradation when pyrene was provided in the form of solid crystals; no effect was observed when the same amount of the chemical was preloaded on polydimethylsiloxane (PDMS). An enhanced effect was observed when pyrene was sorbed into soil but not with the dissolved compound. Synchronous fluorescence spectrophotometry and liquid scintillation were used to determine the phase exchange of pyrene. We also investigated the phase distribution of bacteria. Our results suggest that the rhamnolipid can enhance the biodegradation of pyrene by micellar solubilization and increase diffusive uptake. These mechanisms increase substrate acquisition by bacterial cells at exposure concentrations well above the half-saturation constant for active uptake. The moderate solubilization of pyrene from PDMS by the rhamnolipid and the prevention of cell attachment may explain the lack of enhancement for pyrene-preloaded PDMS.
authors.affiliation: Instituto de Recursos Naturales y Agrobiología (IRNAS), C.S.I.C., Apartado 1052, E-41080, Seville, Spain.
authors.forename: Eleonora
authors.initials: E
authors.lastname: Congiu
authors.affiliation: Institute for Biodiversity and Ecosystem Dynamics (IBED), University of Amsterdam, Science Park 904, 1098 XE 94248, Amsterdam, 1092 GE, The Netherlands.
authors.forename: John R
authors.initials: JR
authors.lastname: Parsons
authors.affiliation: Instituto de Recursos Naturales y Agrobiología (IRNAS), C.S.I.C., Apartado 1052, E-41080, Seville, Spain. Electronic address: jjortega@irnase.csic.es.
authors.forename: José-Julio
authors.initials: JJ
authors.lastname: Ortega-Calvo
mesh_terms: D001673:Biodegradation, Environmental; D001682:Biological Availability; D006017:Glycolipids / Q000737:chemistry*; D009170:Nontuberculous Mycobacteria / Q000378:metabolism*; D011721:Pyrenes / Q000378:metabolism*; D012989:Soil Pollutants / Q000378:metabolism*
chemical_list: D006017:Glycolipids; D011721:Pyrenes; D012989:Soil Pollutants; C418382:rhamnolipid; C030984:pyrene
keywords: Biodegradation; Biosurfactant; Dissolution; Pyrene; Rhamnolipid; Synchronous fluorescence