Dijkhuizen Group

-We study the Physiology/biotechnology of Gram-positive (probiotic) bacteria, of the genera Lactobacillus, Bifidobacterium, Rhodococcus, Mycobacterium, Streptomyces. Various research lines have been developed:

a) synthesis of primary and secondary (e.g. antibiotics) metabolites (Streptomyces);

b) catabolism of steroids/sterols (Rhodococcus, Mycobacterium);

c) synthesis and structural characterization (glycosidic linkages, degree of polymerization, size) of (prebiotic) oligo/polysaccharides by glucansucrase (reuteran, alternan, dextran, Gluco-oligosaccharides), fructansucrase (inulin, levan, Fructo-oligosaccharides) and β-galactosidase (Galacto-oligosacharides) enzymes;

d) analysis of oligo/polysaccharide digestibility by mammalian gastro-intestinal tract enzymes, and their metabolic utilization by gut bacteria. High throughput screening methods have been developed, e.g. using microtiterplates for analysis of glucose/fructose/galactose release, and analysis of bacterial growth using microtiter plate readers.

A major activity also is the study of the structure-function relationships of starch/sucrose/lactose acting enzymes, and the structural analysis of carbohydrate substrates/products. This work involves characterization of novel enzymes, and enzyme engineering of their substrate/product specificity. Novel starch acting enzymes degrading starch granules (involving multiple CBMs and Fibronectins) have been characterized from Microbacterium aurum. In recent years enzymes representing new (sub)families in between GH13/GH70 (GtfB, GtfC, GtfD) have been characterized. They cleave ( α 1-4) linkages in amylose/starch and introduce new ( α 1-6) or ( α 1-3 linkages), resulting in linear or branched α -glucan products. These novel starch based α-glucans represent dietary fibres with potential health benefits through controlled glucose release in the human gastrointestinal tract.