Authors:G. Farkas, J.M. Rezessy-Szabó, F. Zákány, and Á. Hoschke
Fermentation trials were conducted in all-malt wort with mixed cultures of SaccharomycescerevisiaeWS 34/70 and one of two non-Saccharomycesyeast strains: Saccharomycodesludwigiiand Torulaspora delbrueckiiDSM 70607. Interactions were observed between the two yeasts during the alcoholic fermentation process started with eight different initial cell ratios ranging from 1:1 to 1:20 (Saccharomyces yeast : non-Saccharomyces yeast). Composition of the medium greatly affected the cell yield, degree of attenuation and ethanol concentration due to the maltose-negative characteristic of the non-Saccharomycesyeast strains. Starting cell ratios had less effect on the outcome of the fermentation experiments. S. cerevisiaelimited the growth of T. delbrueckiito a great extent, overgrowing it in the course of fermentation. On the other hand, S. cerevisiaedid not grow as dynamically in mixed culture with S. ludwigiias the composition of the medium would have suggested.
Authors:J. M. Rezessy-Szabó, E. Bujna, and Á. Hoschke
a-Galactosidase activity from Thermomyces lanuginosus strain of CBS 395.62/b was investigated in cultivation media with various compositions. Among the seven nitrogen sources only three L-asparagine, yeast extract and ammonium acetate supported the a-galactosidase synthesis. Ammonium acetate proved to be the best candidate as nitrogen source. When glucose or galactose was used as main carbon source, very low level, constitutive a-galactosidase activity was observed. In presence of raffinose, considerable a-galactosidase activity was detected. Raffinose can be replaced by sucrose in the cultivation medium, because the productivity reached by it was superior to that of raffinose. a-Galactosidase activity was improved by the optimisation of the concentrations of sucrose and ammonium acetate in the medium. Applying medium composition with 3% (w/v) sucrose and 0.6% (w/v) ammonium acetate led to at least 5 times higher activity which was observed in the reference medium containing 1.5% (w/v) raffinose and 0.45% (w/v) L-asparagine.
Authors:K. Szekér, J. Beczner, A. Halász, Á. Mayer, J.M. Rezessy-Szabó, and P. Gálfi
The adhesion of twenty-six Lactobacillusstrains to two intestinal cell lines (Caco-2P and IEC-18) and 21 Bifidobacteriumstrains to Caco-2P cells was investigated. Non-specific adherence was determined on the surface of culture plates. The effect of short chain fatty acids (SCFA) on epithelial cells, and bacterial adhesion were investigated by Na-n-butyrate treatment. The adherence of LAB and bifidobacteria greatly varied in a strain-dependent manner. The adherence of LAB was better to IEC-18 cells than to Caco-2P cells, and bifidobacteria adhered better to Caco-2P cells than the LAB. Some strains adhered well or even better to the background than to the cells, which queries the specificity of adhesion of these strains. Na-n-butyrate treatment stimulated the differentiation of IEC-18 cells and therefore increased the number of adherent bacteria, probably because only the cell surface increased not the number of epitopes.