Open Access Pub publishes peer-reviewed, free-to-read open-access articles. Showing
articles matching benzoate — open any to read the full text,
or download the PDF or XML.
P. Solyanikova InnaCorresponding author Laboratory of enzymatic degradation of organic compounds, G.K. Skryabin Institute of Biochemistry and Physiology of Microorganisms of the Russian Academy of Sciences, Pushchino, Russia.
We explored the effect of a change in substrate-benzoate (as sole carbon and energy source) concentration in growth medium on the activity of benzoate 1,2-dioxygenase (BDO) of R.opacus 1CP cells, where BDO is the enzyme mediated the initial attack of benzoate. The activity of the enzyme was estimated by a change of respiration of whole freshly harvested bacterial cells (growth of the cells on benzoate) in response to injection of benzoate. It was shown that when concentration of growth substrate-benzoate decreased from 6 g/L to 250 mg/L, the curves of the dependency of the response rate to benzoate on the initial concentration of benzoate demonstrated that kinetics of the process changes from hyperbolic saturation kinetics, or typical Michaelis-Menten kinetics, to sigmoidal dependency of V on S. The semisaturation constant as a characteristic of the strength of substrate binding with BDO changed simultaneously. These changes were accompanied by the increase in the Hill coefficient from 1.02 up to 3.06, hence positive kinetic cooperativity by a substrate was observed for BDO of R.opacus 1CP cells. The influence of this type of cooperativity on viability of rhodococcus in natural environment and causes of the changes mentioned are discussed. It was hypothesized that an increase in substrate concentration in the medium for the growth of the bacterium not only stimulated synthesis of the inducible enzyme (BDO) in the cell but also led to the change in BDO conformation followed by the change in interaction between substrate-binding active sites of enzymes.
Aljerf LoaiCorresponding author Department of Life Sciences, Faculty of Dentistry, University of Damascus
p-hydroxybenzoic acid esters are used as food and drug preservatives. These compounds were quantised by a reversed-phase thin-layer chromatography method based on the use of silanized silica gel as stationary phase. Thin layers chromatography of silanized silica gel (HF254) is implemented to separate p-hydroxybenzoic acid and its methyl, ethyl, propyl, butyl and benzyl esters. Borate buffer (pH 2) was used as a mobile phase with the addition of organic solvent as required. For the quantitative determination, the solutions to be analysed were applied in bands on 5 x 20 cm plates. The plates are developed in glass chromatography chambers lined with filter paper. After the plates have been developed they are dried at room temperature. The spots or bands of the various compounds are visualised under a 250-mµ UV light source. The extraction of the silica gel with methanol was effective. Six preservatives were separated with better results for benzyl- and butyl-p-hydroxybenzoates. Chromatographic development controlled by temperature stability in the chromatographic chamber and spectrophotometric determination of all the compounds were indicated. A second development with the same solvent mixture was suggested especially when low RF is involved. Various compounds are completely separated and a good determination of p-hydroxybenzoic acid and its principle esters are possible using a simple technique of elution and spectrophotometric determination.