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Zhou K.,Leuven Food Science and Nutrition Research Center oe | Aertsen A.,Leuven Food Science and Nutrition Research Center oe | Michiels C.W.,Leuven Food Science and Nutrition Research Center oe
FEMS Microbiology Reviews | Year: 2014

DNA tandem repeats (TRs), also designated as satellite DNA, are inter- or intragenic nucleotide sequences that are repeated two or more times in a head-to-tail manner. Because TR tracts are prone to strand-slippage replication and recombination events that cause the TR copy number to increase or decrease, loci containing TRs are hypermutable. An increasing number of examples illustrate that bacteria can exploit this instability of TRs to reversibly shut down or modulate the function of specific genes, allowing them to adapt to changing environments on short evolutionary time scales without an increased overall mutation rate. In this review, we discuss the prevalence and distribution of inter- and intragenic TRs in bacteria and the mechanisms of their instability. In addition, we review evidence demonstrating a role of TR variations in bacterial adaptation strategies, ranging from immune evasion and tissue tropism to the modulation of environmental stress tolerance. Nevertheless, while bioinformatic analysis reveals that most bacterial genomes contain a few up to several dozens of intra- and intergenic TRs, only a small fraction of these have been functionally studied to date. © 2013 Federation of European Microbiological Societies. Source

Luu-Thi H.,Leuven Food Science and Nutrition Research Center oe | Khadka D.B.,Leuven Food Science and Nutrition Research Center oe | Michiels C.W.,Leuven Food Science and Nutrition Research Center oe
International Journal of Food Microbiology | Year: 2014

The thermal inactivation kinetics of spores from 39 Bacillus cereus strains belonging to six different phylogenetic groups (group II to VII) was studied. Fresh spore suspensions in glass capillaries were heated in an oil bath at three or more different temperatures for five different times. Survival curves and thermal death curves were established and the kinetic parameters DT (decimal reduction time at temperature T) and z (temperature dependence of DT) were derived by linear regression. Most strains (38/39) had survival curves without a pronounced shoulder or tail, as reflected by linear regression coefficients R2 generally higher than 0.95. The heat resistance of the strains and groups of strains was then compared by determining the temperature (°C) at which logD=0.8 (TlogD=0.8). Spores from group VI strains showed significantly lower heat resistance than all other groups except group II, with TlogD=0.8 ranging between 82.7°C and 92.8°C. Spores from groups III and VII, on the other hand, were generally most heat resistant, with TlogD=0.8 between 91.9°C and 101.8°C. Further analysis revealed a positive correlation between spore heat resistance and both minimal and maximal growth temperatures of the strains. In contrast, the z value was negatively correlated with the minimal and maximal growth temperatures. The availability of genetic group-specific heat resistance data will contribute to a more accurate risk assessment of B. cereus. © 2014 Elsevier B.V. Source

Di Bartolomeo F.,Leuven Food Science and Nutrition Research Center oe | Di Bartolomeo F.,University of Molise | Startek J.B.,Leuven Food Science and Nutrition Research Center oe | Van Den Ende W.,Leuven Food Science and Nutrition Research Center oe
Phytotherapy Research | Year: 2013

Bacteria living in the gastrointestinal tract are crucial for human health and disease occurrence. Increasing the beneficial intestinal microflora by consumption of prebiotics, which are 'functional foods', could be an elegant way to limit the number and incidence of disorders and to recover from dysbiosis or antibiotic treatments. This review focuses on the short-chain low-digestible carbohydrates (LDCs) which are metabolized by gut microbiota serving as energy source, immune system enhancers or facilitators of mineral uptake. Intake of foods containing LDCs can improve the state of health and may prevent diseases as for example certain forms of cancer. Given the large number of different molecules belonging to LDCs, we focused our attention on fructans (inulin, fructo-oligosaccharides), galacto-oligosaccharides and resistant starches and their therapeutic and protective applications. Evidence is accumulating that LDCs can inhibit bacterial and viral infections by modulating host defense responses and by changing the interactions between pathogenic and beneficial bacteria. Animal studies and studies on small groups of human subjects suggest that LDCs might help to counteract colorectal cancer, diabetes and metabolic syndrome. The action mechanisms of LDCs in the human body might be broader than originally thought, perhaps also including reactive oxygen species scavenging and signaling events. © 2012 John Wiley & Sons, Ltd. Source

Palmero P.,Leuven Food Science and Nutrition Research Center oe | Lemmens L.,Leuven Food Science and Nutrition Research Center oe | Hendrickx M.,Leuven Food Science and Nutrition Research Center oe | Van Loey A.,Leuven Food Science and Nutrition Research Center oe
Food Chemistry | Year: 2014

Cell walls and chromoplast substructures constitute natural structural barriers governing carotenoid bioaccessibility. In order to enhance carotenoid bioaccessibility, thermal processes were applied to fractions surrounded by different levels of structural barriers. The matrices studied were orange carrots, red carrots, red tomatoes and atomic red carrots. In the case of carrots, no effect of thermal treatments on carotenoid bioaccessibility at the chromoplast level was obtained. However, in the case of tomatoes, lycopene bioaccessibility decreased upon thermal processing of chromoplasts. At the cell cluster level, low intensities of thermal processing resulted in a decrease of β-carotene and lycopene bioaccessibility. Nonetheless, at high intensities of thermal processing, only β-carotene bioaccessibility was increased. This observation was confirmed by the results obtained in the matrix rich in both types of carotenoids (atomic red carrots). It was therefore suggested, that the type of carotenoid constitutes an important factor determining the effect of thermal processing on their bioaccessibility. © 2014 Elsevier Ltd. All rights reserved. Source

Pauly A.,Leuven Food Science and Nutrition Research Center oe | Pareyt B.,Leuven Food Science and Nutrition Research Center oe | Fierens E.,Leuven Food Science and Nutrition Research Center oe | Delcour J.A.,Leuven Food Science and Nutrition Research Center oe
Comprehensive Reviews in Food Science and Food Safety | Year: 2013

Wheat kernel hardness is a major quality characteristic used in classifying wheat cultivars. Differences in endosperm texture among Triticum aestivum L. or between T. aestivum and T. turgidum L. ssp. durum cultivars profoundly affect their milling behavior, the properties of the obtained flour or semolina particles, as well as the quality of products made thereof. It is now widely accepted that the presence, sequence polymorphism, or absence of the basic and cysteine-rich puroindolines a and b are responsible for differences in endosperm texture. These proteins show features in vitro, including foaming and lipid-binding properties, which provide them with a potential impact in the production of wheat-based food products, where they may improve gas cell stabilization or modulate interactions between starch, proteins, and/or lipids. We here summarize the impact of wheat hardness on milling properties and bread, cookie, cake, and pasta quality and discuss the role of puroindolines therein. © 2013 Institute of Food Technologists®. Source

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