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.
Production of phytase by Aspergillus niger F00735 strain in submerged fermentation was studied. The effects of various natural substrates with different phytate contents on secretion of extracellular phytase were investigated and the rice flour with about 5 mg g−1 of phytic acid was found to be the best one. The repression effect of high levels of phytic acid or inorganic phosphorous in fermentation medium (corn flour, wheat grit, soy flour, etc.) on production of phytase was also observed. The optimal concentration of rice flour as main carbon sourc e was determined in combination with sodium nitrate. The maximal activity (≈1500 U l−1, 1.5 times higher than using basal medium) was achieved on the 7th day in media containing 7.12% (w/v) rice flour and 0.86% (w/v) sodium nitrate. Supplementation of fermentation medium with different surfactants such as Tween series (20, 40, 60, 65, 80, 85) and Triton X-100 up to 0.1% (w/v) had no significant effects on the secretion of phytase enzyme, meanwhile at concentrations higher than 0.2% (w/v), decrease in enzyme activity was observed.
Effects of mixed cultures of Saccharomyces cerevisiae Levuline FB — higher ethanol tolerance — and different Kluyveromyces strains — higher inulinase activity — on the production of ethanol from Jerusalem artichoke extract were investigated. Among the investigated strains, combination of S. cerevisiae and K. marxianus strain Y00959 with simultaneous saccharification and fermentation gave the best efficiency (76%) of bioconversion. The optimal ratio of mixed cultures was determined to be 1:1 of K. marxianus and S. cerevisiae. Central composite design (CCD) was adapted to find the optimum initial substrate concentration and inoculum size for the maximal production of ethanol from Jerusalem artichoke juice. The optimum fermentation conditions were found to be 24% (m/w) substrate concentration and 45 OD600nm ml/100 ml inoculum size of mixed culture. Use of these conditions, about 10.67% (v/v) was produced at 148 h of alcoholic fermentation given. Results of this work provide benefits of mixed culture on production of bioethanol from Jerusalem artichoke.
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.
Twenty-six Bifidobacterium strains were isolated from human faeces. Seven strains were identified as B. bifidum, 4 strains as B. breve, 10 strains as B. longum, 2 strains as B. pseudocatenulatum and 3 strains as B. dentium by 16S rDNA analysis. The isolates from human origin showed strong adherence to the human tissue cultures. Three out of the 12 tested isolates repressed the growth of enteropathogenic bacteria. Utilisation of 9 commercially available oligosaccharides was tested by both Bifidobacteria and enteropathogens. Pro-, pre- and synbiotic food was made. Their effect was evaluated in in vivo feeding experiments, where healthy and antibiotic treated mice were used as test animals. During the four-week feeding period the composition of the colonic microbiota of the healthy mice did not change characteristically in any feeding group. However, the microbiota of mice in which it had been killed by antibiotic treatment was recovered by feeding with synbiotic food.
Consumers are becoming more interested in healthy nutrition. To meet consumer requirements, the possibility of the fruit and vegetable juice fermentation by bifidobacteria was investigated. Sour cherry, orange, carrot, and tomato juice was fermented with five Bifidobacterium strains (from human origin and starter culture). The tested strains have grown well in orange, carrot, and tomato juices. The B. longum Bb-46 strain demonstrated the best growth activities. It was found that ratio of the produced acetic and lactic acids are dependent on the Bifidobacterium strain rather than on the fermentation medium. The most intensive inhibition was observed against the Campylobacter jejuni strain. In course of the fermentation the antioxidant capacities slightly decreased, except when the orange juice was fermented with B. lactis Bb-12 and B. longum A4.8. The obtained results may contribute to the design of a novel functional food product.
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.