Ingeborg C. Boels

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Lactococcus lactis produced more exopolysaccharide (EPS) on glucose than on fructose as the sugar substrate, although the transcription level of the eps gene cluster was independent of the sugar source. A major difference between cells grown on the two substrates was the capacity to produce sugar nucleotides, the EPS precursors. However, the activities of(More)
We studied the UDP-glucose pyrophosphorylase (galU) and UDP-galactose epimerase (galE) genes of Lactococcus lactis MG1363 to investigate their involvement in biosynthesis of UDP-glucose and UDP-galactose, which are precursors of glucose- and galactose-containing exopolysaccharides (EPS) in L. lactis. The lactococcal galU gene was identified by a PCR(More)
The relationships between glucose metabolism and exopolysaccharide (EPS) production in a Lactococcus lactis strain containing the EPS gene cluster (Eps(+)) and in nonproducer strain MG5267 (Eps(-)) were characterized. The concentrations of relevant phosphorylated intermediates in EPS and cell wall biosynthetic pathways or glycolysis were determined by (31)P(More)
We describe the effects of modulating the activities of glucokinase, phosphofructokinase, and phosphoglucomutase on the branching point between sugar degradation and the biosynthesis of sugar nucleotides involved in the production of exopolysaccharide biosynthesis by Lactococcus lactis. This was realized by using a described isogenic L. lactis mutant with(More)
The aim of this work was to investigate the medium requirements for growth and production of exopolysaccharides by Lactobacillus delbrueckii subsp. bulgaricus NCFB 2772. The strain was grown in batch cultures on a chemically defined medium, and the technique of single omission of medium components was applied to determine the nutritional requirements. The(More)
dTDP-rhamnose is an important precursor of cell wall polysaccharides and rhamnose-containing exopolysaccharides (EPS) in Lactococcus lactis. We cloned the rfbACBD operon from L. lactis MG1363, which comprises four genes involved in dTDP-rhamnose biosynthesis. When expressed in Escherichia coli, the lactococcal rfbACBD genes could sustain heterologous(More)
The lactic acid bacteria Lactococcus lactis and Streptococcus thermophilus play a crucial role in the manufacture of dairy products such as cheese, buttermilk and yogurt. In this contribution, different metabolic engineering strategies are described aimed at improvement of the quality of the fermented dairy product. By increased production of diacetyl or(More)
Lactic acid bacteria display a relatively simple and well described metabolism where the sugar source is converted mainly to lactic acid. Here we will shortly describe metabolic engineering strategies that led to the efficient re-routing of the lactococcal pyruvate metabolism to end-products other than lactic acid, including diacetyl and alanine. Moreover,(More)
Microbial exopolysaccharides (EPSs) are used in the food industry for their unique properties as viscosifiers, stabilisers, emulsifiers or gelling agents. In recent years, significant progress in the understanding of the genetics and biochemistry of microbial EPS synthesis by both Gram-negative and Gram-positive bacteria has been made. Biosynthesis pathways(More)
Over the last years, important advances have been made in the study of the production of exopolysaccharides (EPS) by several lactic acid bacteria, including Lactococcus lactis. From different EPS-producing lactococcal strains the specific eps gene clusters have been characterised. They contain eps genes, which are involved in EPS repeating unit synthesis,(More)