130 research outputs found
Handboek Nederlands-Antilliaans omgevingsrecht. Inleiding tot het recht inzake milieu, natuur en ruimtelijke ontwikkeling op de Nederlandse Antillen
Using Lactococcus lactis for glutathione overproduction
Glutathione and -glutamylcysteine were produced in Lactococcus lactis using a controlled expression system and the genes gshA and gshB from Escherichia coli encoding the enzymes -glutamylcysteine synthetase and glutathione synthetase. High levels of -glutamylcysteine were found in strains growing on chemically defined medium and expressing either gshA alone or both gshA and gshB. As anticipated, glutathione was found in a strain expressing gshA and gshB. The level of glutathione production could be increased by addition of the precursor amino acid cysteine to the medium. The addition of cysteine led to an increased activity of glutathione synthetase, which is remarkable because the amino acid is not a substrate of this enzyme. The final intracellular glutathione concentration attained was 358 nmol mg¿1 protein, which is the highest concentration reported for a bacterium, demonstrating the suitability of engineered L. lactis for fine-chemical production and as a model for studies of the impact of glutathione on flavour formation and other properties of food
Safe use of genetically modified lactic acid bacteria in food. Bridging the gap between consumers, green groups, and industry
Within the European Union (EU), the use of genetically modified
organisms (GMOs) in food production is not widely applied and accepted.
In contrast to the United States of America, the current EU legislation
limits the introduction of functional foods derived from GMOs that may
bring a clear benefit to the consumer. Genetically modified lactic acid
bacteria (GM-LAB) can be considered as a different class of GMOs, and
the European Union is preparing regulations for the risk assessment of
genetically modified microorganisms. Since these procedures are not yet
implemented, the current risk assessment procedure is shared for GMOs
derived from micro organisms, plants, or animals. At present, the use
of organisms in food production that have uncontrolled genetic
alterations made through random mutagenesis, is permitted, while
similar applications with organisms that have controlled genetic
alterations are not allowed. The current paper reviews the
opportunities that genetically modified lactic acid bacteria may offer
the food industry and the consumer. An objective risk profile is
described for the use of GM-LAB in food production. To enhance the
introduction of functional foods with proven health claims it is
proposed to adapt the current safety assessment procedures for (GM)-LAB
and suggestions are made for the related cost accountability. A
qualified presumption of safety as proposed by SANCO (EU SANCO 2003),
based on taxonomy and on the history of safe use of LAB applied in
food, could in the near future be applied to any kind of LAB or GM-LAB
provided that a series of modern profiling methods are used to verify
the absence of unintended effects of altered LAB that may cause harm to
the health of the consumer
Evidence of a Massive Black Hole Companion in the Massive Eclipsing Binary V Puppis
Up to now, most stellar-mass black holes were discovered in X-ray emitting
binaries, in which the black holes are formed through a common-envelope evolu
tion. Here we give evidence for the presence of a massive black hole candidate
as a tertiary companion in the massive eclipsing binary V Puppis. We found that
the orbital period of this short-period binary (P=1.45 days) shows a periodic
variation while it undergoes a long-term increase. The cyclic period
oscillation can be interpreted by the light-travel time effect via the presence
of a third body with a mass no less than 10.4 solar mass. However, no spectral
lines of the third body were discovered indicating that it is a massive black
hole candidate. The black hole candidate may correspond to the weak X-ray
source close to V Puppis discovered by Uhuru, Copernicus, and ROSAT satellites
produced by accreting materials from the massive binary via stellar wind. The
circumstellar matter with many heavy elements around this binary may be formed
by the supernova explosion of the progenitor of the massive black hole. All of
the observations suggest that a massive black hole is orbiting the massive
close binary V Puppis with a period of 5.47 years. Meanwhile, we found the
central close binary is undergoing slow mass transfer from the secondary to the
primary star on a nuclear time scale of the secondary component, revealing that
the system has passed through a rapid mass-transfer stage.Comment: Accepted for publication in ApJ
MY Camelopardalis, a very massive merger progenitor
Context. The early-type binary MY Cam belongs to the young open cluster
Alicante 1, embedded in Cam OB3. Aims. MY Cam consists of two early-O type
main-sequence stars and shows a photometric modulation suggesting an orbital
period slightly above one day. We intend to confirm this orbital period and
derive orbital and stellar parameters. Methods. Timing analysis of a very
exhaustive (4607 points) light curve indicates a period of 1.1754514 +-
0.0000015 d. High- resolution spectra and the cross-correlation technique
implemented in the TODCOR program were used to derive radial velocities and
obtain the corresponding radial velocity curves for MY Cam. Modelling with the
stellar atmosphere code FASTWIND was used to obtain stellar parameters and
create templates for cross-correlation. Stellar and orbital parameters were
derived using the Wilson-Devinney code, such that a complete solution to the
binary system could be described. Results. The determined masses of the primary
and secondary stars in MY Cam are 37.7 +- 1.6 and 31.6 +- 1.4 Msol,
respectively. The corresponding temperatures, derived from the model atmosphere
fit, are 42 000 and 39 000 K, with the more massive component being hotter.
Both stars are overfilling their Roche lobes, sharing a common envelope.
Conclusions. MY Cam contains the most massive dwarf O-type stars found so far
in an eclipsing binary. Both components are still on the main sequence, and
probably not far from the zero-age main sequence. The system is a likely merger
progenitor, owing to its very short period.Comment: 8 pages, 6 figures, photometric data available on-line, Astronomy and
Astrophysics, 201
A novel consortium of Lactobacillus rhamnosus and Streptococcus thermophilus for increased access to functional fermented foods
Background: The lactic acid bacterium Lactobacillus rhamnosus GG is the most studied probiotic bacterium with proven health benefits upon oral intake, including the alleviation of diarrhea. The mission of the Yoba for Life foundation is to provide impoverished communities in Africa increased access to Lactobacillus rhamnosus GG under the name Lactobacillus rhamnosus yoba 2012, world's first generic probiotic strain. We have been able to overcome the strain's limitations to grow in food matrices like milk, by formulating a dried starter consortium with Streptococcus thermophilus that enables the propagation of both strains in milk and other food matrices. The affordable seed culture is used by people in resource-poor communities. Results: We used S. thermophilus C106 as an adjuvant culture for the propagation of L. rhamnosus yoba 2012 in a variety of fermented foods up to concentrations, because of its endogenous proteolytic activity, ability to degrade lactose and other synergistic effects. Subsequently, L. rhamnosus could reach final titers of 1E+09 CFU ml(-1), which is sufficient to comply with the recommended daily dose for probiotics. The specific metabolic interactions between the two strains were derived from the full genome sequences of L. rhamnosus GG and S. thermophilus C106. The piliation of the L. rhamnosus yoba 2012, required for epithelial adhesion and inflammatory signaling in the human host, was stable during growth in milk for two rounds of fermentation. Sachets prepared with the two strains, yoba 2012 and C106, retained viability for at least 2 years. Conclusions: A stable dried seed culture has been developed which facilitates local and low-cost production of a wide range of fermented foods that subsequently act as delivery vehicles for beneficial bacteria to communities in east Africa.Peer reviewe
- …