19F MRI oximetry: simulation of perfluorocarbon distribution impact.

In (19)F MRI oximetry, a method used to image tumour hypoxia, perfluorocarbons serve as oxygenation markers. The goal of this study is to evaluate the impact of perfluorocarbon distribution and concentration in (19)F MRI oximetry through a computer simulation. The simulation studies the correspondence between (19)F measured (pO(FNMR)(2)) and actual tissue oxygen tension (pO(2)) for several tissue perfluorocarbon distributions. For this, a Krogh tissue model is implemented which incorporates the presence of perfluorocarbons in blood and tissue. That is, in tissue the perfluorocarbons are distributed homogeneously according to Gaussian diffusion profiles, or the perfluorocarbons are concentrated in the capillary wall. Using these distributions, the oxygen tension in the simulation volume is calculated. The simulated mean oxygen tension is then compared with pO(FNMR)(2), the (19)F MRI-based measure of pO(2) and with pO(0)(2), pO(2) in the absence of perfluorocarbons. The agreement between pO(FNMR)(2) and actual pO(2) is influenced by vascular density and perfluorocarbon distribution. The presence of perfluorocarbons generally gives rise to a pO(2) increase in tissue. This effect is enhanced when perfluorocarbons are also present in blood. Only the homogeneous perfluorocarbon distribution in tissue with no perfluorocarbons in blood guarantees small deviations of pO(FNMR)(2) from pO(2). Hence, perfluorocarbon distribution in tissue and blood has a serious impact on the reliability of (19)F MRI-based measures of oxygen tension. In addition, the presence of perfluorocarbons influences the actual oxygen tension. This finding may be of great importance for further development of (19)F MRI oximetry.

Radio-physical properties of micelle leucodye 3D integrating gel dosimeters.

Recently, novel radiochromic leucodye micelle hydrogel dosimeters were introduced in the literature. In these studies, gel measured electron depth dose profiles were compared with ion chamber depth dose data, from which it was concluded that leucocrystal violet-type dosimeters were independent of dose rate. Similar conclusions were drawn for leucomalachite green-type dosimeters, only after pre-irradiating the samples to a homogeneous radiation dose. However, in our extensive study of the radio-physical properties of leucocrystal violet- and leucomalachite green-type dosimeters, a significant dose rate dependence was found. For a dose rate variation between 50 and 400 cGy min(-1), a maximum difference of 75% was found in optical dose sensitivity for the leucomalachite green-type dosimeter. Furthermore, the measured optical dose sensitivity of the leucomalachite green-type dosimeter was four times lower than the value previously reported in the literature. For the leucocrystal violet-type dosimeter, a maximum difference in optical dose sensitivity of 55% was found between 50 and 400 cGy min(-1). A modified composition of the leucomalachite green-type dosimeter is proposed. This dosimeter is composed of gelatin, sodium dodecyl sulfate, chloroform, trichloroacetic acid and leucomalachite green. The optical dose sensitivity amounted to 4.375 × 10(-5) cm(-1) cGy(-1) (dose rate 400 cGy min(-1)). No energy dependence for photon energies between 6 and 18 MV was found. No temperature dependence during readout was found notwithstanding a temperature dependence during irradiation of 1.90 cGy °C(-1) increase on a total dose of 100 cGy. The novel gel dosimeter formulation exhibits an improved spatial stability (2.45 × 10(-7) cm(2) s(-1) (= 0.088 mm(2) h(-1))) and good water/soft tissue equivalence. Nevertheless, the novel formulation was also found to have a significant, albeit reduced, dose rate dependence, as a maximum difference of 33% was found in optical dose sensitivity when the dose rate varied between 50 and 400 cGy min(-1). By pre-irradiating the novel leucomalachite green-type dosimeter to 500 cGy, the apparent difference in dose response between 200 and 400 cGy min(-1) was eliminated, similar to earlier findings. However, a dose response difference of 38% between 50 and 200 cGy min(-1) was still measured. On the basis of these experimental results it is concluded that the leucodye micelle gel dosimeter is not yet optimal for dose verifications of high precision radiation therapy treatments. This study, however, indicates that the dose rate dependence has a potential for improvement. Future research is necessary to further minimize the dose rate dependence through extensive chemical analysis and optimization of the gel formulation. Some insights into the physicochemical mechanisms were obtained and are discussed in this paper.

Degradation of isooctane by Mycobacterium austroafricanum IFP 2173: growth and catabolic pathway.

AIMS: Isooctane (2,2,4-trimethylpentane), a major component of gasoline formulations, is recalcitrant to biodegradation probably because of the quaternary carbon group it contains. Information on the biodegradability of this hydrocarbon is essential to evaluate its fate in the environment. For these reasons, the degradation kinetics and the catabolic pathway of isooctane were investigated in Mycobacterium austroafricanum IFP 2173, the only strain characterized to use it as sole carbon and energy source. METHODS AND RESULTS: The selected strain exhibited a rather moderate maximum growth rate (micromax = 0.053 h(-1)) but degraded isooctane up to 99% with a mineralization yield of 45%, indicating attack of the quaternary carbon group. The GC/MS identification of metabolites, 2,4,4-trimethylpentanoic and dimethylpropanoic (pivalic) acids, which transiently accumulated in the cultures indicated that degradation started from the isopropyl extremity of the molecule and subsequently proceeded by catabolism of the tert-butyl moiety. The degradation of putative metabolic intermediates was investigated. The initial isooctane oxidation system was tentatively characterized. CONCLUSIONS: The isooctane-degrading strain harboured two candidate systems for initial alkane oxidation. Although a cytochrome P450 was induced by isooctane degradation, the functional oxidation system was probably a nonheme alkane monooxygenase as indicated by PCR amplification and RT-PCR expression of an alkB gene. SIGNIFICANCE AND IMPACT OF THE STUDY: Isooctane is a recalcitrant branched alkane. A plausible pathway of its degradation by Myco. austroafricanum was put forward.

Microbial degradation and fate in the environment of methyl tert-butyl ether and related fuel oxygenates.

Oxygenates, mainly methyl tert-butyl ether (MTBE), are commonly added to gasoline to enhance octane index and improve combustion efficiency. Other oxygenates used as gasoline additives are ethers such as ethyl tert-butyl ether (ETBE), tert-amyl methyl ether (TAME), and alcohols such as tert-butyl alcohol (TBA). As a result of its wide use, MTBE has been detected, mainly in the USA, in groundwater and surface waters, and is a cause of concern because of its possible health effects and other undesirable consequences. MTBE is a water-soluble and mobile compound that generates long pollution plumes in aquifers impacted by gasoline releases from leaking tanks. Field observations concur in estimating that, because of recalcitrance to biodegradation, natural attenuation is slow (half-life of at least 2 years). However, quite significant advances have been made in recent years concerning the microbiology of the degradation of MTBE and other oxygenated gasoline additives. The recalcitrance of these compounds results from the presence in their structure of an ether bond and of a tertiary carbon structure. For the most part, only aerobic microbial degradation systems have been reported so far. Consortia capable of mineralizing MTBE have been selected. Multiple instances of the cometabolism of MTBE with pure strains or with microflorae, growing on n-alkanes, isoalkanes, cyclohexane or ethers (diethyl ether, ETBE), have been described. MTBE was converted into TBA in all cases and was sometimes further degraded, but it was not used as a carbon source by the pure strains. However, mineralization of MTBE and TBA by several pure bacterial strains using these compounds as sole carbon and energy source has recently been reported. The pathways of metabolism of MTBE involve the initial attack by a monooxygenase. In several cases, the enzyme was characterized as a cytochrome P-450. After oxygenation, the release of a C -unit as formaldehyde or formate leads to the production of TBA, which can be converted to 2-hydroxyisobutyric acid and further metabolized. Developments in microbiology make biological treatment of water contaminated with MTBE and other oxygenates an attractive possibility. Work concerning ex situ treatment in biofilters by consortia and by pure strains, and involving or not cometabolism, is under way. Furthermore, the development of in situ treatment processes is a promisinggoal.

Biodegradation of tert-butyl alcohol and related xenobiotics by a methylotrophic bacterial isolate.

A new aerobic bacterial strain, CIP 1-2052, isolated from an activated sludge sample, was able to use tert-butyl alcohol (TBA), a product of methyl tert-butyl ether (MTBE) and ethyl tert-butyl ether (ETBE) degradation, as its sole carbon and energy source. Cobalt ions stimulated TBA mineralization. The maximum growth and TBA degradation rates were 0.032 +/- 0.004 h(-1) and 35.8 +/- 8.5 mg TBA x g(-1) (cell dry mass) per h, respectively. The growth yield on TBA was 0.54 +/- 0.02 g x g(-1). Strain CIP 1-2052 exhibited a particular substrate specificity towards alcohols. It degraded tertiary alcohols, TBA and tert-amyl alcohol (TAA), but neither their primary and secondary alcohol homologues, nor ethanol. However, one-carbon compounds, namely methanol and formate, were degraded by strain CIP 1-2052, showing the methylotrophic nature of this isolate. The properties of this new strain suggest that it could be used for bioremediation of contaminated aquifers.

Biodegradation of ethyl t-butyl ether (ETBE), methyl t-butyl ether (MTBE) and t-amyl methyl ether (TAME) by Gordonia terrae.

Gordonia terrae strain IFP 2001 was selected from activated sludge for its capacity to grow on ethyl t-butyl ether (ETBE) as sole carbon and energy source. ETBE was stoichiometrically degraded to t-butyl alcohol (TBA) and the activity was inducible. A constitutive strain, G. terrae IFP 2007, derived from strain IFP 2001, was also selected. Methyl t-butyl ether (MTBE) and t-amyl methyl ether (TAME) were not used as carbon and energy sources by the two strains, but cometabolic degradation of MTBE and TAME was demonstrated, to TBA and t-amyl alcohol (TAA) respectively, in the presence of a carbon source such as ethanol. No two-carbon compound was detected during growth on ETBE, but formate was produced during cometabolic degradation of MTBE or TAME. A monooxygenase was involved in the degradation of ethers, because no degradation of ETBE was observed under anaerobic conditions and the presence of a cytochrome P-450 was demonstrated in G. terrae IFP 2001 after induction by cultivation on ETBE.

Biodegradability of volatile hydrocarbons of gasoline.

The biodegradability under aerobic conditions of volatile hydrocarbons (4-6 carbons) contained in gasoline and consisting of n-alkanes, iso-alkanes, cycloalkanes and alkenes, was investigated. Activated sludge was used as the reference microflora. The biodegradation test involved the degradation of the volatile fraction of gasoline in closed flasks under optimal conditions. The kinetics of biodegradation was monitored by CO2 production. Final degradation was determined by gas chromatographic analysis of all measurable hydrocarbons (12 compounds) in the mixture after sampling the headspace of the flasks. The degradation of individual hydrocarbons was also studied with the same methodology. When incubated individually, all hydrocarbons used as carbon sources, except 2,2-dimethylbutane and 2,3-dimethylbutane, were completely consumed in 30 days or less with different velocities and initial lag periods. When incubated together as constituents of the light gasoline fraction, all hydrocarbons were metabolised, often with higher velocities than for individual compounds. Cometabolism was involved in the degradation of dimethyl isoalkanes.

A Mycobacterium strain with extended capacities for degradation of gasoline hydrocarbons.

A bacterial strain (strain IFP 2173) was selected from a gasoline-polluted aquifer on the basis of its capacity to use 2,2, 4-trimethylpentane (isooctane) as a sole carbon and energy source. This isolate, the first isolate with this capacity to be characterized, was identified by 16S ribosomal DNA analysis, and 100% sequence identity with a reference strain of Mycobacterium austroafricanum was found. Mycobacterium sp. strain IFP 2173 used an unusually wide spectrum of hydrocarbons as growth substrates, including n-alkanes and multimethyl-substituted isoalkanes with chains ranging from 5 to 16 carbon atoms long, as well as substituted monoaromatic hydrocarbons. It also attacked ethers, such as methyl t-butyl ether. During growth on gasoline, it degraded 86% of the substrate. Our results indicated that strain IFP 2173 was capable of degrading 3-methyl groups, possibly by a carboxylation and deacetylation mechanism. Evidence that it attacked the quaternary carbon atom structure by an as-yet-undefined mechanism during growth on 2,2,4-trimethylpentane and 2,2-dimethylpentane was also obtained.

Selection of microbial populations degrading recalcitrant hydrocarbons of gasoline by monitoring of culture-headspace composition.

A methodology was devised and was found useful for the selection of populations degrading recalcitrant hydrocarbons. The work was part of a programme aiming at developing knowledge of the intrinsic capacities of autochtonous microflorae of the environment for gasoline biodegradation. The methodology involved monitoring the progress of degradation in enrichment liquid cultures on the selected hydrocarbon by gas chromatographic analysis of CO2 production and O2 consumption. Populations degrading in particular o-xylene, 1,2,4-trimethylbenzene, cyclohexane were obtained. Concerning 2,2,4-trimethylpentane (isooctane), one microflora (and a pure strain derived from it) growing on this hydrocarbon were obtained from gasoline-polluted water.

Distribution in the environment of degradative capacities for gasoline attenuation.

A methodology allowing the detailed assessment of the capacities of microflorae to degrade gasoline in aerobic conditions has been developed. It consisted in the determination of the degradation of a gasoline model mixture in liquid cultures in optimal conditions. The gasoline model mixture contained 23 representative hydrocarbons of gasoline (GM23). The kinetics and extent of biodegradation were evaluated by continuous overall monitoring of CO2 production and final chromatographic analysis (usually after about 30 days) of the consumption of each hydrocarbon. The methodology was used with soil and water samples from polluted and non polluted sites. The experimentation aimed at assessing the distribution of the degradative capacities in the environment and the prospects for natural attenuation of gasoline. Nine microflorae were tested. The intrinsic biodegradability (existence of mechanisms of biodegradation) appeared total for GM23 as shown by the results obtained with several microflorae. The degradative capacities of microflorae from non polluted samples were high (total degradation rates at least 85%). Incomplete degradation was observed essentially for trimethylalkanes (2,2,4-trimethylpentane and 2,3,4-trimethylpentane) and for cyclohexane. In several cases, samples from polluted sites exhibited more extensive degradative capacities, with total degradation of all hydrocarbons being observed for three out of the six samples.

Biodegradation of gasoline: kinetics, mass balance and fate of individual hydrocarbons.

The degradation of gasoline by a microflora from an urban waste water activated sludge was investigated in detail. Degradation kinetics were studied in liquid cultures at 30 degrees C by determination of overall O2 consumption and CO2 production and by chromatographic analysis of all 83 identifiable compounds. In a first fast phase (2 d) of biodegradation, 74% of gasoline, involving mostly aromatic hydrocarbons, was consumed. A further 20%, involving other hydrocarbons, was consumed in a second slow phase (23 d). Undegraded compounds (6% of gasoline) were essentially some branched alkanes with a quaternary carbon or/and alkyl chains on consecutive carbons but cycloalkanes, alkenes and C10- and C11-alkylated benzenes were degraded. The degradation kinetics of individual hydrocarbons, determined in separate incubations, followed patterns similar to those observed in cultures on gasoline. Carbon balance experiments of gasoline degradation were performed. The carbon of degraded gasoline was mainly (61.7%) mineralized into CO2, the remaining carbon being essentially converted into biomass.

Diversity of bacterial strains degrading hexadecane in relation to the mode of substrate uptake.

The relative distribution of the modes of hydrocarbon uptake, used by bacteria of the environment for the degradation of long-chain alkanes, has been evaluated. The first mode of uptake, direct interfacial accession, involves contact of cells with hydrocarbon droplets. In the second mode, biosurfactant-mediated transfer, cell contact takes place with hydrocarbons emulsified or solubilized by biosurfactants. Sixty-one strains growing on hexadecane were isolated from polluted and non-polluted soils and identified. The majority (61%) belonged to the Corynebacterium-Mycobacterium-Nocardia group. Criteria selected for characterizing hexadecane uptake were cell hydrophobicity, interfacial and surface tensions and production of glycolipidic extracellular biosurfactants. These properties were determined in flask cultures on an insoluble (hexadecane) and on a soluble (glycerol or succinate) carbon source for a subset of 23 representative strains. Exclusive direct interfacial uptake was utilized by 47% of studied strains. A large proportion of strains (53%) produced biosurfactants. The data on cellular hydrophobicity suggested the existence of two distinct alkane transfer mechanisms in this group. Accordingly, tentative assignments of biosurfactant-mediated micellar transfer were made for 11% of the isolated strains, and of biosurfactant-enhanced interfacial uptake for 42%.

Efficiency of defined strains and of soil consortia in the biodegradation of polycyclic aromatic hydrocarbon (PAH) mixtures.

The microbiological characteristics of the bacterial degradation of mixtures of five polycyclic aromatic hydrocarbons (PAH), phenanthrene, fluorene, anthracene, fluoranthene and pyrene, were investigated. Three pure bacterial strains using one or several of these PAH as carbon sources were selected. The interactions between PAH during the degradation of PAH pairs by each of these strains were studied and their effects on the kinetics and the balance of degradation were characterised. Competition between PAH and degradation by cometabolism were frequently observed. Mixed cultures of two or three strains, although possessing the global capacity to mineralise the set of five PAH, achieved limited degradation of the mixture. In contrast, a consortium from a PAH-contaminated soil readily mineralised the five-PAH mixture. The results suggested that soil consortia possessed a wider variety of strains capable to compensate for the competitive inhibition between PAH as well as specialised strains that mineralised potentially inhibitory PAH metabolites produced by cometabolism.

Involvement of a rhamnolipid-producing strain of Pseudomonas aeruginosa in the degradation of polycyclic aromatic hydrocarbons by a bacterial community.

A rhamnolipid-producing strain of Pseudomonas aeruginosa GL1 was isolated from a bacterial community growing on a mixture of polycyclic aromatic hydrocarbons (PAH) as sole carbon source. Strain GL1 did not grow on PAH but grew on known degradation metabolites of phenanthrene (O-phthalic acid) and of naphthalene (salicylic acid). In co-culture with a phenanthrene-degrading strain, Ps. aeruginosa GL1 accelerated the degradation of phenanthrene. Strain GL1 was resistant to toxic amphiphilic compounds such as cationic and anionic detergents. Rhamnolipid production took place in a late stage growth in cultures of strain GL1 on glycerol or n-hexadecane. It coincided with a substantial decrease in cell hydrophobicity and with morphological changes of the outer membrane as observed by transmission electronic microscopy. The rhamnolipids produced inhibited the growth of bacteria such as Rhodococcus erythropolis, Bacillus cereus and Ps. fluorescens. The overall results suggested an outer membrane origin for the rhamnolipids. They also indicate that the utilization of PAH metabolites by strain GL1 is important for the stability of the PAH-degrading community.

Intrinsic capacities of soil microflorae for gasoline degradation.

A methodology to determine the intrinsic capacities of a microflora to degrade gasoline was developed, in particular for assessing the potential of autochtonous populations of polluted and non polluted soils for natural attenuation and engineered bioremediation. A model mixture (GM23) constituted of the 23 most representative hydrocarbons of a commercial gasoline was used. The capacities of the microflorae (kinetics and extent of biodegradation) were assessed by chromatographic analysis of hydrocarbon consumption and of CO2 production. The degradation of the components of GM23 was assayed in separate incubations of each component and in the complete mixture. For the microflora of an unpolluted spruce forest soil, all hydrocarbons of GM23 except cyclohexane, 2,2,4- and 2,3,4-trimethylpentane isomers were degraded to below detection limit in 28 days. This microflora was reinforced with two mixed microbial communities selected from gasoline-polluted sites and shown to degrade cyclohexane and 2,2,4-trimethylpentane. With the reinforced microflora, complete degradation of GM23 was observed. The degradation patterns of individual components of GM23 were similar when the compounds were present individually or in the GM23 mixture, as long as the concentrations of 2-ethyltoluene and trimethylbenzene isomers were kept sufficiently low (< or = 35 mg.l-1) to remain below their inhibitory level.

Kinetic studies of biodegradation of insoluble compounds by continuous determination of oxygen consumption.

Continuous determination of oxygen consumption by electrolytic respirometry has been experimented as a means to study the biodegradation kinetics of scarcely soluble environmental pollutants. The substrates used were the polycyclic aromatic hydrocarbons (PAH), naphthalene, phenanthrene, anthracene, fluoranthene and pyrene. The definition of an appropriate mode of PAH supply, either as crystals or more generally as a solution in a water non-miscible solvent, was found essential for yielding reproducible biodegradation kinetics. In these conditions, for all compounds tested, oxygen determination was found suitable for quantitative evaluation of PAH biodegradation and formation of biomass and soluble metabolites. The study of biodegradation kinetics with this methodology showed that a first phase of exponential growth could be characterized in most cases, followed by a phase of limited growth. Possible mechanisms involved in insoluble substrate uptake are discussed. During exponential growth, the bacteria utilized (although not necessarily exclusively) the PAH solubilized in the aqueous medium.

The microbiological fate of polycyclic aromatic hydrocarbons: carbon and oxygen balances for bacterial degradation of model compounds.

A series of pure bacterial strains belonging mainly to the Rhodococcus and Pseudomonas genera were grown on one of the following polycyclic aromatic hydrocarbons (PAH) supplied as sole carbon and energy source; naphthalene, fluorene, phenanthrene, anthracene, fluoranthene and pyrene. In each case, a quantitative evaluation of the carbon repartition of the PAH degraded into CO2, biomass and water-soluble metabolites was carried out. In addition, the kinetics of oxygen consumption and of water-soluble metabolite accumulation during PAH biodegradation was followed with respirometric equipment. Satisfactory carbon balances were obtained and the data correlated well with oxygen consumption values. The results show that growth on PAH presents high mineralization yields (from 56% to 77% of carbon) and sizeable production of biomass (from 16% to 35% of carbon) and limited but significant accumulation of metabolites (from 5% to 23% of carbon). The mineralization yields were higher and biomass yields lower in the case of higher PAH. Some differences between strains were also observed.

Substrate availability in phenanthrene biodegradation: transfer mechanism and influence on metabolism.

The mechanism of phenanthrene transfer to the bacteria during biodegradation by a Pseudomonas strain was investigated using a sensitive respirometric technique (Sapromat equipment) allowing the quasi-continuous acquisition of data on oxygen consumption. Several systems of phenanthrene supply, crystalline solid and solutions in non-water-miscible solvents (silicone oil and 2,2,4,4,6,8,8-heptamethylnonane) were studied. In all cases, analysis of the kinetics of oxygen consumption demonstrated an initial phase of exponential growth with the same specific growth rate. In order to analyze the second phase of growth and phenanthrene degradation, a study of the kinetics of phenanthrene transfer to the aqueous phase was conducted by direct experimentation, with the crystal and silicone oil systems, in abiotic conditions. The data allowed the validation of a model based on phase-transfer laws, describing the variations, with substrate concentrations, of rates of phenanthrene transfer to the aqueous phase. Analysis of the biodegradation curves then showed that exponential growth ended in all cases when the rates of phenanthrene consumption reached the maximal transfer rates. Thereafter, the biodegradation rates closely obeyed, for all systems, the transfer rate values given by the model. These results unambiguously demonstrated that, in the present case, phenanthrene biodegradation required prior transfer to the aqueous phase. With the silicone oil system, which allowed high transfer and biodegradation rates, phenanthrene was directed towards higher metabolite production and lower mineralization, as shown by oxygen consumption and carbon balance determinations.

Degradation of polycyclic aromatic hydrocarbons by pure strains and by defined strain associations: inhibition phenomena and cometabolism.

Six bacterial strains capable of using, as sole carbon and energy source, at least one of the following polycyclic aromatic hydrocarbons (PAH), naphthalene, fluorene, phenanthrene, anthracene, fluoranthene and pyrene, were isolated. The interactions between these PAH during their biodegradation were studied in experiments involving PAH pairs, one PAH at least being used as a carbon source. All individual strains were found capable of cometabolic degradation of PAH in a range varying among strains. Inhibition phenomena, sometimes drastic, were often observed but synergistic interactions were also detected. Naphthalene was toxic to all strains not isolated on this compound. Strain associations were found efficient in relieving inhibition phenomena, including the toxic effect of naphthalene. Accumulation of water-soluble metabolites was consistently observed during PAH degradation.

Identification and determination of individual sophorolipids in fermentation products by gradient elution high-performance liquid chromatography with evaporative light-scattering detection.

High-performance liquid chromatography (HPLC) was used for the characterization of sophorolipids, one of the most important types of glycolipid biosurfactants. By using gradient elution with a water-acetonitrile mixture on a reversed-phase (C18) column and evaporative light-scattering detection, resolution of all the important individual sophorolipids present in fermentation products was achieved. In addition to HPLC, a combination of techniques involving selective production by fermentation of sophorolipids, chemical conversions of the products, separation methods and, for identification of lipidic chains of sophorolipids, gas chromatography and mass spectrometry was used. This led to the identification of almost all significant compounds observed in HPLC, including several previously unreported sophorolipids. As a result, a rapid method is now available for investigations of the influence of fermentation conditions on the nature and quantitative distribution of the sophorolipid products obtained.