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Erick J Vandamme

Publications and source records attributed to Erick J Vandamme.

7 recordsLinked to original sources
PubMed2005

Boric acid as a mobile phase additive for high performance liquid chromatography separation of ribose, arabinose and ribulose.

A new high performance liquid chromatographic (HPLC) method is described for the analysis of ribose, arabinose and ribulose mixtures obtained from (bio)chemical isomerization processes. These processes gain importance since the molecules can be used for the synthesis of antiviral therapeutics. The HPLC method uses boric acid as a mobile phase additive to enhance the separation on an Aminex HPX-87K column. By complexing with boric acid, the carbohydrates become negatively charged, thus elute faster from the column by means of ion exlusion and are separated because the complexation capacity with boric acid differs from one carbohydrate to another. Excellent separation between ribose, ribulose and arabinose was achieved with concentrations between 0.1 and 10 gL(-1) of discrete sugar.

Aldose-Ketose Isomerases↗
PubMed2005

Dextran dextrinase and dextran of Gluconobacter oxydans.

Certain strains of Gluconobacter oxydans have been known since the 1940s to produce the enzyme dextran dextrinase (DDase; EC2.4.1.2)-a transglucosidase converting maltodextrins into (oligo)dextran. The enzyme catalyses the transfer of an alpha1,4 linked glucosyl unit from a donor to an acceptor molecule, forming an alpha1,6 linkage: consecutive glucosyl transfers result in the formation of high molecular weight dextran from maltodextrins. In the early 1990s, the group of K. Yamamoto in Japan revived research on DDase, focussing on the purification and characterisation of the intracellular DDase produced by G. oxydans ATCC 11894. More recently, this was taken further by Y. Suzuki and coworkers, who investigated the properties and kinetics of the extracellular DDase formed by the same strain. Our group further elaborated on fermentation processes to optimise DDase production and dextran formation, DDase characterisation and its use as a biocatalyst, and the physiological link between intracellular and extracellular DDase. Here, we present a condensed overview of the current scientific status and the application potential of G. oxydans DDase and its products, (oligo)dextrans. The production of DDase as well as of dextran is first described via optimised fermentation processes. Specific assays for measuring DDase activity are also outlined. The general characteristics, substrate specificity, and mode of action of DDase as a transglucosidase are described in detail. Two forms of DDase are produced by G. oxydans depending on nutritional fermentation conditions: an intracellular and an extracellular form. The relationship between the two enzyme forms is also discussed. Furthermore, applications of DDase, e.g. production of (oligo)dextran, transglucosylated products and speciality oligosaccharides, are summarized.

Biotechnology↗
PubMed2005

Gluconobacter oxydans NAD-dependent, D-fructose reducing, polyol dehydrogenases activity: screening, medium optimisation and application for enzymatic polyol production.

Gluconobacter oxydans LMG 1489 was selected as the best strain for NAD(P)-dependent polyol dehydrogenase production. The highest enzyme activities were obtained when this strain was cultivated on a medium consisting of 30 g glycerol l(-1), 7.2 g peptone l(-1) and 1.8 g yeast extract l(-1). Two D-fructose reducing, NAD-dependent intracellular enzymes were present in the G. oxydans cell-free extract: sorbitol dehydrogenase, and mannitol dehydrogenase. Substrate reduction occurred optimally at a low pH (pH 6), while the optimum for substrate oxidation was situated at alkaline pHs (pH 9.5-10.5). The mannitol dehydrogenase was more thermostable than the sorbitol dehydrogenase. The cell-free extract could be used to produce D-mannitol and D-sorbitol enzymatically from D-fructose. Efficient coenzyme regeneration was accomplished by formate dehydrogenase-mediated oxidation of formate into CO2.

Biotechnology↗
PubMed2004

Potential of selected lactic acid bacteria to produce food compatible antifungal metabolites.

The aim of this study was to assess the potential of lactic acid bacteria to inhibit the outgrowth of some common food-spoiling fungi. Culture supernatants of 17 Lactic acid bacterial strains as well as of three commercial probiotic cultures were evaluated for antifungal activity using an agar-diffusion method. The method parameters were chosen in order to reveal compounds for potential use in food (bio)preservation. Thirteen strains showed antifungal activity of which five strains were very promising: Lactobacillus acidophilus LMG 9433, L. amylovorus DSM 20532, L. brevis LMG 6906, L. coryniformis subsp. coryniformis LMG 9196 and L. plantarum LMG 6907. Four of these five strains were further examined; it was found that the produced antifungal metabolites were pH-dependent. The exact chemical nature of these substances has not been revealed yet.

Antibiosis↗
PubMed2003

Multiple forms of microbial enzymes.

Multiple forms of one enzyme occur in a wide variety of microorganisms. Their synthesis is often dependent on culture characteristics such as medium composition, physico-chemical parameters, culture age and the presence of inducing or inhibiting agents. Multiform enzymes increase the capability of the producing organism to adapt to and cope with a wide variety of environmental changes, such that the physiological advantages outweigh the apparent wasteful hyperproduction of multiple forms of one enzyme.

Adaptation, Biological↗
PubMedDate not supplied

Optimization of ectoine synthesis through fed-batch fermentation of Brevibacterium epidermis.

A production process for ectoine has been developed, using Brevibacterium epidermis DSM20659 as the producer strain. First, the optimal conditions for intracellular synthesis of ectoine were determined. The size of the intracellular ectoine pool is shown to be dependent on the external salt concentration, type of carbon source, and yeast extract concentration. Under the optimized conditions of 1 M NaCl, 50 g/L monosodium glutamate, and 2.5 g/L yeast extract, a maximum concentration of intracellular ectoine of 0.9 g/L was obtained in shake flask cultures. After optimizing the batch fermentation parameters of temperature, pH, agitation, and aeration, the yield could be further increased by applying the fed-batch fermentation principle in 1.5- to 2-L fermentors. Glutamate and yeast extract were fed to the bacterial cells such that the total glutamate concentration in the broth remained constant. A total yield of 8 g ectoine/L fermentation broth was obtained with a productivity of 2 g ectoine/L/day. After the bacterial cells were harvested from the culture broth, the ectoine was recovered from them by a two-step extraction with water and ethanol. Crystallization of the product was obtained after concentration of the extract via evaporation under reduced pressure. After this downstream process, 55% of the ectoine produced in the fermentor could be crystallized in four fractions. The first fractions were of very high purity (98%). This production process can compete with other described production processes for ectoine in productivity and simplicity. Further advantages are the relatively low amounts of NaCl needed and the absence of hydroxyectoine, often a byproduct, in the final product.

Air↗