| 1. |
- van Niel, Ed, et al.
(författare)
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The potential of biodetoxification activity as a probiotic property of Lactobacillus reuteri.
- 2012
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Ingår i: International Journal of Food Microbiology. - : Elsevier BV. - 0168-1605. ; 152, s. 206-210
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Tidskriftsartikel (refereegranskat)abstract
- Previous work on the metabolism of Lactobacillus reuteri ATCC 55730 anticipated a variability in the use of organic electron acceptors as a means to relieve metabolic redox problems. Therefore, investigations focusing on this unique metabolism of L. reuteri may reveal a basis for new probiotic properties. For instance, L. reuteri may use reactive aldehydes and ketones as electron acceptors to balance their redox metabolism, which opens the possibility to exploit this bacterium for in vivo bioreduction of deleterious compounds in the gastrointestinal tract (GIT). Herein we demonstrate that L. reuteri ATCC 55730 cultures on glucose are able to use furfural (1g/L), and hydroxymethylfurfural (HMF) (0.5g/L), as electron acceptors. The former enhances the growth rate by about 25% and biomass yield by 15%, whereas the latter is inhibitory. Furfural is stoichiometrically reduced to furfuryl alcohol by the culture. The conversion of furfural had no effect on the flux distribution between the simultaneously operating phosphoketolase and Embden-Meyerhof pathways, but initiated a flux to acetate production. In addition to furfural and HMF, cellular extracts showed potential to reoxidize NADH and/or NADPH with acrolein, crotonaldehyde, and diacetyl, indicating that conversion reactions take place intracellularly, however, utilization mechanisms for the latter compounds may not be present in this strain. The strain did not reduce other GIT-related reactive compounds, including acrylamide, glyoxal, and furan.
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| 2. |
- Velasco, Susana, et al.
(författare)
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Environmental factors influencing growth of and exopolysaccharide formation by Pediococcus parvulus 2.6
- 2006
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Ingår i: International Journal of Food Microbiology. - : Elsevier BV. - 0168-1605. ; 111:3, s. 252-258
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Tidskriftsartikel (refereegranskat)abstract
- Natural exopolysaccharides (EPSs) from food-grade lactic acid bacteria have potential for development and exploitation as food additives and functional food ingredients with both health and economic benefits. In this study, we have examined the physiological capacity of EPS production in Pediococcus parvulus 2.6. EPS formation by P. parvulus 2.6 was found to be linked to biomass yields, provided that glucose was not limiting. Higher biomass yields and EPS productions were obtained when cultures were pH-controlled at pH 5.2. Various compounds have been tested for their influence on growth rate and EPS formation. Of those, only glucose (up to 75 g 1(-1)), ethanol (up to 4.9%, w/v) and glycerol (up to 6.6%, w/v) had positive effects on EPS production. EPS production was not directly linked to growth, because its production continued in the stationary phase provided that glucose was present. According to an empirical model, the growth of R parvulus 2.6 was completely inhibited by 58.9 +/- 18.1 gl(-1) lactate. Lactate, the sole fermentation product, was suggested to affect growth by chelation of manganese. The organism grew in an apparent linear fashion due to this imposed manganese limitation. This could be overcome by increasing the manganese concentration to at least 2 mg l(-1) in the medium. The excretion of Mn2+ upon depletion of glucose indicated that maintenance of the high Mn2+ gradient over the cell membrane is an energy requiring process. EPS production was increased from 0.12 gl(-1) to 4.10 gl(-1) in an improved medium that is based on the results from this study. (c) 2006 Elsevier B.V. All rights reserved.
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| 3. |
- Årsköld, Emma, et al.
(författare)
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Environmental influences on exopolysaccharide formation in Lactobacillus reuteri ATCC 55730.
- 2007
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Ingår i: International Journal of Food Microbiology. - : Elsevier BV. - 0168-1605. ; 116:1, s. 159-167
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Tidskriftsartikel (refereegranskat)abstract
- Lactobacillus reuteri is known to produce exopolysaccharides (EPS), which have the potential to be used as an alternative biothickener in the food industry. In this study, the effect of several environmental conditions on the growth and EPS production in the L. reuteri strain ATCC 55730 was determined. The expression of the corresponding reuteransucrase gene, gtfO, was investigated over time and the results indicated that the expression increased with growth during the exponential phase and subsequently decreased in the stationary phase. Fermentation with glucose and/or sucrose as carbon and energy source revealed that gtfO was constitutively expressed and that the activity profile was independent of the sugar source. In the applied ranges of parameter values, temperature and pH were the most important factors for EPS formation and only temperature for growth. The best EPS yield, 1.4 g g(-1) CDW, was obtained at the conditions 37 degrees C, pH 4.5 and 100 g l(-1) sucrose, which were close to the estimated optimal conditions: pH 4.56 and 100 g l(-1) sucrose. No EPS formation could be detected with glucose. In addition, no direct connection between the expression and the activity of reuteransucrase could be established. Finally, the strain ATCC 55730 was benchmarked against 14 other L. reuteri strains with respect to EPS production from sucrose and abilities to metabolise sucrose, glucose and fructose. Eight strains were able to produce glucan and a corresponding glucansucrase gene was confirmed for each of them. (c) 2007 Elsevier B.V. All rights reserved.
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