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The degradation of alkanes and alcohols by Rhodococcus erythropolis DCL14 growing cells was tested at different reactor scales, ranging from a 2-L fermenter to 300 μL 96-well plates. The highest growth rates were attained in the fermenter, where pH, temperature and aeration rate, in particular, are monitored and controlled. However, the results acquired in reactors smaller than 100 mL indicate that these reactors may be successfully used in testing carbon sources, since the normalized results obtained with the different carbons sources were maintained in the 100-0.3 mL range. This study also shows the great potential of R. erythropolis DCL14 cells to degrade a wide range of alcohols and alkanes, which may be used in bioremediation of contaminated sites. [ABSTRACT FROM AUTHOR]

The behaviour of cells of Rhodococcus erythropolis DCL14, Xanthobacter Py2, Arthrobacter simplex and Mycobacterium sp. NRRL B-3805, in biphasic systems containing different organic solvents was evaluated and compared. The data, obtained mainly by fluorescence microscopy and image analysis, was interpreted using principal components analysis (PCA). With this technique, the variability of the data could be summarised in 7 components, representing 75.8% of the variance of the data. Over a third of the variance could be explained by the first two principal components which represent solvent toxicity. Apparently this is the major factor influencing cell behaviour in an organic:aqueous system. However, factors such as substrate concentration, cell adaptation ability (resulting in morphological changes and aggregation or separation of cells) and membrane composition (specific to each strain) also play an important role in cell resistance to solvent toxicity. The results regarding cell shape indicate that loss of viability occurs, in the tested bacterial strains, after incorporation of molecules of solvent in the cellular membrane. This should result in an increase in membrane fluidity, and thus, in an alteration of cell shape. The ability to form "self-defence" clusters was observed to be different amongst the four strains. X. Py2 showed, in general, a low tendency to form aggregates under the tested conditions; A. simplex and R. erythropolis aggregated mainly in the presence of low log P solvents; and Mycobacterium. sp. cells showed a high ability to aggregate. [ABSTRACT FROM AUTHOR]

The effect of some solvents, present in different amounts, upon whole cells of Rhodococcus erythropolis DCL14 carrying out the biotransformation of (-)-carveol to (-)-carvone was studied. The solvents tested were ethyl butyrate, n -hexane, cyclohexane, iso -octane, n -dodecane, dimethyl sulfoxide, bis(2-ethylhexyl) phthalate and FC-70. The volumes of each solvent corresponded to organic:aqueous phase ratios of 0.0005, 0.0025, 0.005, 0.025 and 0.2. To assess any potential solvent protection towards substrate toxicity, assays were carried out at two initial carveol concentrations (15 and 50 mM). Carvone accumulation was followed by gas chromatography. Cell viability, several aspects of cell morphology and the ability to form clusters were monitored by fluorescence microscopy. Principal components analysis (PCA) was used as a tool to explain the differences in the observations of the multidimensional data set obtained from the multiple conditions. PCA using the different volumes of each solvent as variable suggests that the variability of the observations can be summarised in six components which represent 79.4% of the variance of the data. Conversely, using cell and solvent data to perform the PCA, 97.1% of the variance of the data can be summarised in three components, the first two capturing 91.0% of the information. These components seem to represent solvent toxicity and a protective effect of the solvent from carveol toxicity. [ABSTRACT FROM AUTHOR]

Develops a genetically engineered Escherichia coli strain for the epoxide hydrolase-catalysed kinetic resolution of epoxides. Evidence of a 138-fold increase in Eph1 activity in cell extracts of the recombinant E. coli; Results of optimization of cultivation conditions and co-expression of molecular chaperones.

A selection of different glycosidases was screened for the glycosylation of 1-propanethiol. The β-glucosidases from almond, Aspergillus niger and Caldocellum saccharolyticum were capable of 1-propanethioglucoside (1-PTG) formation. The almond β-glucosidase showed the highest activity in this reversed hydrolysis type of reaction using glucose as glucosyl donor. Besides 1-propanethiol, also thioglucosides of 2-propanethiol and furfuryl mercaptan were formed by the almond β-glucosidase. The substrate specificity of the almond β-glucosidase with respect to thioglucosylation is restricted to primary and secondary aliphatic thiols. Once the thioglucosides are formed, they are not hydrolyzed at a significant rate by almond β-glucosidase. As a consequence the synthesis of 1-PTG could be observed at very low aglycone concentrations (0.5% v/v based on the reaction solution) and high yields (68% based on 1-PT and 41% based on glucose) were obtained. An excess of aglycone, otherwise frequently applied in reversed hydrolysis glycosylation, is therefore not necessary in the glucosylation of 1-PT. [ABSTRACT FROM AUTHOR]

Pseudomonas putida MC2 can be used to produce catechols. The accumulation, specific and volumetric production rates of 3-methylcatechol from toluene have been studied. Production rates were shown to depend on growth medium, pH and toluene concentration. Minimal glucose medium and rich LB medium were the best growth media for 3-methylcatechol production. A lower pH often resulted in slower growth and a higher specific production rate, but a lower volumetric production rate. Specific production rates also increased at higher initial toluene concentrations. The best process conditions in terms of substrate conversion and specific production rate were found in minimal glucose medium at an initial aqueous toluene concentration of 1.0 mM and an initial pH of 6. At pH 7 and 2.0 mM toluene, more product was accumulated at a lower specific rate, but at a higher volumetric production rate. [ABSTRACT FROM AUTHOR]