Yasmine Delaedt

Structurally different wheat-derived arabinoxylooligosaccharides have different prebiotic and fermentation properties in rats.

To evaluate the prebiotic potential and intestinal fermentation products of wheat bran-derived arabinoxylooligosaccharides (AXOS) in relation to their structure, 5 preparations with structurally different AXOS were included ( approximately 4% wt:wt) in rat diets that mimicked the average Western human diet composition. Xylooligosaccharides (XOS), fructooligosaccharides (FOS), and inulin were used as references. The observed effects mainly depended on the average degree of polymerization (avDP) of the AXOS preparations. The AXOS and XOS preparations with a low avDP (<or=3) resulted in increased colonic acetate and butyrate production and boosted bifidobacteria concentrations in the cecum, but did not significantly lower the concentrations of branched SCFA, which are considered to be markers of protein fermentation by intestinal microbiota. In contrast, an AXOS preparation with a higher avDP (61) effectively suppressed branched SCFA concentrations and thus tipped the balance away from protein fermentation. However, it neither increased colonic butyrate concentrations nor stimulated cecal bifidobacteria development. Two AXOS preparations with a similar avDP (12 and 15) but different average degrees of arabinose substitution (avDAS) (0.69 and 0.27) affected the measured intestinal characteristics similarly, suggesting that the influence of the avDAS was apparently limited and possibly overshadowed by that of the avDP. Among those tested, an AXOS preparation with an avDP of 5 and an avDAS of 0.27 exhibited the best combination of desirable effects on gut health characteristics. Compared with this optimal AXOS preparation, FOS and inulin resulted in similar bifidogenic effects with increased production of colonic acetate (inulin) but not of butyrate. These new insights into the structure-activity relation of AXOS open up new perspectives for the production and application of AXOS preparations with optimized prebiotic and fermentation properties.

Tolerance of arabinoxylan-oligosaccharides and their prebiotic activity in healthy subjects: a randomised, placebo-controlled cross-over study.

The tolerance and prebiotic effect following oral intake by healthy human subjects of arabinoxylan-oligosaccharides (AXOS), produced by partial enzymic hydrolysis of the wheat fibre arabinoxlyan, were studied. A total of twenty healthy subjects participated in the present randomised, placebo-controlled cross-over study. They consumed 10 g AXOS or placebo per d each for 3 weeks with a 4-week wash-out period in between. Before and immediately after each intake period, blood samples were taken to measure haematological and clinical chemistry parameters and the subjects completed a questionnaire about gastrointestinal symptoms. Additionally, urine was collected over 48 h for analysis of p-cresol and phenol content by GC-MS, and faeces were collected over 72 h for analysis of microbiota using real-time PCR. Of the subjects, ten also performed a urine and faeces collection 2 weeks after the start of intake (during intervention). A limited number of tested blood parameters were influenced in a statistically significantly way by either AXOS or placebo intake, but these changes remained within the normal range. Blood lipids remained unchanged. AXOS had no statistically significant effect on the range of gastrointestinal symptoms, except for a mild increase in flatulence. Urinary p-cresol excretion, an indicator of protein fermentation, was significantly decreased after 2 weeks of AXOS intake. The levels of bifidobacteria were significantly increased after 2 and 3 weeks of AXOS intake as well as after 3 weeks of placebo. However, the effect of AXOS on bifidobacteria was more pronounced than that of placebo. In conclusion, AXOS are a well-tolerated prebiotic at the dose of 10 g/d. AXOS intake increases faecal bifidobacteria and reduces urinary p-cresol excretion.

Evaluation of process parameters of ultrasonic treatment of bacterial suspensions in a pilot scale water disinfection system

In this study, several process parameters that may contribute to the efficiency of ultrasound disinfection are examined on a pilot scale water disinfection system that mimics realistic circumstances as encountered in an industrial environment. The main parameters of sonication are: (i) power; (ii) duration of treatment; (iii) volume of the treated sample. The specific energy (E(s)) is an indicator of the intensity of the ultrasound treatment because it incorporates the transferred power, the duration of sonication and the treated volume. In this study, the importance of this parameter for the disinfection efficiency was assessed through changes in volume of treated water, water flow rate and electrical power of the ultrasonic reactor. In addition, the influences of the initial bacterial concentration on the disinfection efficiency were examined. The disinfection efficiency of the ultrasonic technique was scored on a homogenous and on a mixed bacterial culture suspended in water with two different types of ultrasonic reactors (Telsonic and Bandelin). This study demonstrates that specific energy, treatment time of water with ultrasound and number of passages through the ultrasonic reactor are crucial influential parameters of ultrasonic disinfection of contaminated water in a pilot scale water disinfection system. The promising results obtained in this study on a pilot scale water disinfection system indicate the possible application of ultrasound technology to reduce bacterial contamination in recirculating process water to an acceptable low level. However, the energy demand of the ultrasound equipment is rather high and therefore it may be advantageous to apply ultrasound in combination with another treatment.

Impact of Non- Legionella Bacteria on the Uptake and Intracellular Replication of Legionella pneumophila in Acanthamoeba castellanii and Naegleria lovaniensis

In aquatic environments, Legionella pneumophila survives, in association with other bacteria, within biofilms by multiplying in free-living amoebae. The precise mechanisms underlying several aspects of the uptake and intracellular replication of L. pneumophila in amoebae, especially in the presence of other bacteria, remain unknown. In the present study, we examined the competitive effect of selected non-Legionella bacteria (Escherichia coli, Aeromonas hydrophila, Flavobacterium breve, and Pseudomonas aeruginosa) on the uptake of L. pneumophila serogroup 1 by the amoebae Acanthamoeba castellanii and Naegleria lovaniensis. We also investigated their possible influence on the intracellular replication of L. pneumophila in both amoeba species. Our results showed that the non-Legionella bacteria did not compete with L. pneumophila for uptake, suggesting that the amoeba hosts took in L. pneumophila through a specific and presumably highly efficient uptake mechanism. Living and heat-inactivated P. aeruginosa best supported the replication of L. pneumophila in N. lovaniensis and A. castellanii, respectively, whereas for both amoeba species, E. coli yielded the lowest number of replicated L. pneumophila. Furthermore, microscopic examination showed that 100% of the A. castellanii and only 2% of the N. lovaniensis population were infected with L. pneumophila at the end of the experiment. This study clearly shows the influence of some non-Legionella bacteria on the intracellular replication of L. pneumophila in A. castellanii and N. lovaniensis. It also demonstrates the different abilities of the two tested amoeba species to serve as a proper host for the replication and distribution of the human pathogen in man-made aquatic environments such as cooling towers, shower heads, and air conditioning systems with potential serious consequences for human health.

Survey for the presence of specific free-living amoebae in cooling waters from Belgian power plants

Free-living amoebae (FLA) are distributed ubiquitously in aquatic environments with increasing importance in hygienic, medical and ecological relationships to man. In this study, water samples from Belgian industrial cooling circuits were quantitatively surveyed for the presence of FLA. Isolated, thermotolerant amoebae were identified morphologically as well as using the following molecular methods: enzyme-linked immunosorbent assay and isoenzyme electrophoresis and PCR. Thermophilic amoebae were present at nearly all collection sites, and the different detection methods gave similar results. Naegleria fowleri was the most frequently encountered thermotolerant species, and concentrations of thermotolerant FLA were correlated with higher temperatures.

Selected nondigestible carbohydrates and prebiotics support the growth of probiotic fish bacteria mono-cultures in vitro

Aims:  To search for nondigestible but fermentable (NDF) carbohydrates and prebiotics with a potency to promote the growth of selected bacteria in vitro.

Quantitative Detection and Differentiation of Free-Living Amoeba Species Using SYBR Green–Based Real-Time PCR Melting Curve Analysis

Real-time polymerase chain reaction melting curve analysis (MCA) allows differentiation of several free-living amoebae species. Distinctive characteristics were found for Naegleria fowleri, N. lovaniensis, N. australiensis, N. gruberi, Hartmanella vermiformis, and Willaertia magna. Species specificity of the amplicons was confirmed using agarose gel electrophoresis and sequence-based approaches. Amplification efficiency ranged from 91% to 98%, indicating the quantitative potential of the assay. This MCA approach can be used for quantitative detection of free-living amoebae after cultivation but also as a culture-independent detection method.