Biomedical subjects

M Manuela R da Fonseca

Publications and source records attributed to M Manuela R da Fonseca.

8 recordsLinked to original sources

PubMed2005

Cell adaptation to solvent, substrate and product: a successful strategy to overcome product inhibition in a bioconversion system.

Carvone has previously been found to highly inhibit its own production at concentrations above 50 mM during conversion of a diastereomeric mixture of (-)-carveol by whole cells of Rhodococcus erythropolis. Adaptation of the cells to the presence of increasing concentrations of carveol and carvone in n-dodecane prior to biotransformation proved successful in overcoming carvone inhibition. By adapting R. erythropolis cells for 197 h, an 8.3-fold increase in carvone production rate compared to non-adapted cells was achieved in an air-driven column reactor. After an incubation period of 268 h, a final carvone concentration of 1.03 M could be attained, together with high productivity [0.19 mg carvone h(-1) (ml organic phase)(-1)] and high yield (0.96 g carvone g carveol(-1)).

Adaptation, Physiological↗

PubMed2005

Biotransformation of terpenes.

The main application of terpenes as fragrances and flavors depends on the absolute configuration of the compounds because enantiomers present different organoleptic properties. Biotransformations allow the production of regio- and stereoselective compounds under mild conditions. These products may be labeled as "natural". Commercially useful chemical building-blocks and pharmaceutical stereo isomers can also be produced by bioconversion of terpenes. Enzymes and extracts from bacteria, cyanobacteria, yeasts, microalgae, fungi, plants, and animal cells have been used for the production and/or bioconversion of terpenes. In addition, whole cell catalysis has also been used. A variety of media and reactors have been assessed for these biotransformations and have produced encouraging results, as discussed in this review.

Bacteria↗

PubMed2005

The remarkable Rhodococcus erythropolis.

Rhodococcus erythropolis cells contain a large set of enzymes that allow them to carry out an enormous number of bioconversions and degradations. Oxidations, dehydrogenations, epoxidations, hydrolysis, hydroxylations, dehalogenations and desulfurisations have been reported to be performed by R. erythropolis cells or enzymes. This large array of enzymes fully justifies the prospective application of this bacterium in biotechnology.

Biodegradation, Environmental↗

PubMed2005

A simple imaging method for biomass determination.

An inexpensive and fast method based on images taken during growth of bacterial cells on multi-well plates was developed for biomass quantification. A correlation of 85% between the results obtained by image analysis and optical density measurements was obtained. This simple method allows the assessment of growth with highly aggregated cell cultures and the rapid screening of a large number of carbon sources.

Alcohols↗

PubMed2004

Degradation of hydrocarbons and alcohols at different temperatures and salinities by Rhodococcus erythropolis DCL14.

Rhodococcus erythropolis DCL14 cells were able to metabolise C5-C16 hydrocarbons and C1-C12 alcohols as sole carbon and energy sources, both at 15 and 28 degrees C. Metabolic activity was also observed at 1.00%, 1.95% and 2.50% sodium chloride. Almost complete degradation of n-, iso- and cyclo-alkanes and aromatic compounds present in fuel oil was achieved after 9 months, 60% being consumed in the first three months. The results from the conditions tested here suggest that this type of bacterium could be involved in bioremediation processes in marine environments such as the Atlantic, Pacific and Indian Ocean.

Alcohols↗

PubMed2004

Adaptation of Rhodococcus erythropolis DCL14 to growth on n-alkanes, alcohols and terpenes.

Rhodococcus erythropolis DCL14 has the ability to convert the terpene (-)-carveol to the valuable flavour compound (-)-carvone when growing on a wide range of carbon sources. To study the effect of carbon and energy sources such as alkanes, alkanols and terpenes on the biotechnological process, the cellular adaptation at the level of fatty acid composition of the membrane phospholipids and the (-)-carvone production were examined. All tested carbon sources caused a dose-dependent increase in the degree of saturation of the fatty acids. The exception was observed with short-chain alcohols such as methanol and ethanol, to which the cells adapted with a concentration-dependent decrease in the saturation degree of the membrane phospholipids. This influence of the different carbon sources on the rigidity of the cell membrane also had an impact on the (-)-carvone productivity of the strain.

Adaptation, Physiological↗

PubMed2004

Solvent toxicity in organic-aqueous systems analysed by multivariate analysis.

The effect of several solvents present in a biphasic reaction system on cells of Rhodococcus erythropolis DCL14, Xanthobacter Py2, Arthrobacter simplex and Mycobacterium sp. NRRL B-3805 was evaluated. These four strains have been widely exploited, from bioremediation to the production of fine chemicals, in two-phase reaction media. The solvents tested were ethyl butyrate, n-hexane, cyclohexane, iso-octane, n-dodecane, DMSO, bis(2-ethylhexyl) phthalate and fluorinert FC-70. The cell population was monitored by fluorescence microscopy and analysis of the images captured provided single-cell-level information on cell viability, morphological factors of both viable and non-viable cells, and on the number of viable cells in clusters. These data, and those concerning the initial carveol concentration, the carbon source used during growth, the adaptation time to the solvent prior to substrate addition, and the properties of the organic solvent, were interpreted using principal components analysis (PCA). For R. erythropolis, X. Py2, and A. simplex, between 70.1 and 80.4% of the variability of the data could be explained by six principal components, while 86.7% of the variance in the results obtained with Mycobacterium sp. could be represented by seven principal components. In all cases, solvent toxicity could explain over a third of the variability in the data. R. erythropolis cells were able to maintain their viability under harsh conditions. A period of contact between cells and solvent, prior to the addition of substrate, was prejudicial for R. erythropolis and A. simplex cells, at least for the most toxic solvents, but was beneficial for X. Py2 cells. The number of Mycobacterium sp. cells in clusters was lower after an adaptation period compared to the number of cells in aggregates when the substrate was added at time zero. The substrates transformed by R. erythropolis and A. simplex cells increased the toxicity of the system by decreasing the log P of the reaction mixture. Hydrocortisone was responsible for a reduction in the ability of A. simplex to respond to stress conditions. Mycobacterium sp. cells were apparently unaffected by beta-sitosterol. The results obtained are useful for the design of more efficient two-phase reaction systems where solvent toxicity may be overcome in order to increase cell productivity.

Algorithms↗

PubMed2004

Mycobacterium sp., Rhodococcus erythropolis, and Pseudomonas putida behavior in the presence of organic solvents.

This work aimed at studying the behavior and tolerance of Mycobacterium sp. NRRL B-3805, Rhodococcus erythropolis DCL14 and Pseudomonas putida S12 cells in the presence of various concentrations of water miscible (ethanol, butanol, and dimethylformamide, up to 50% v/v) and water immiscible solvents (dodecane, bis(2-ethylhexyl) phthalate and toluene, up to 5% v/v). When incubated in the presence of these solvents, the cells were found to have lower tolerance to butanol and toluene than to the remaining solvents. Nevertheless, the concentrations of solvents endured by the tested strains show that they are quite solvent-tolerant, confirming their potential as biocatalysts in nonconventional systems. Microscopic observation of samples showed that the hydrophobic Mycobacterium sp. and R. erythropolis cells were able to aggregate to protect the population under stress conditions. Comparison of the results obtained at the single cell level by fluorescence microscopy and colony development on agar plates indicated that the primary effects of most solvents tested were on the cell membrane and replicating capability of the cells.

Cell Aggregation↗