39 research outputs found
Improving the Quality of European Hard Cheese by controlling interactions between Lactic Acid Bacteria and Propionic Acid Bacteria (LAB/PAB) (Stimulation of Propionic Acid Bacteria by Lactic
End of Project ReportTeagasc acknowledges with gratitude grant aid under the EU Framework Programme (FAIR
96-CT-1024).In the manufacture of Swiss-type cheese two successive fermentations
occur. During manufacture, lactic acid bacteria (LAB), particularly
Streptococcus thermophilus, Lactobacillus helveticus and
Lb. delbrueckii subsp. lactis, convert lactose to lactate while,
during ripening, propionic acid bacteria (PAB) convert lactate to
propionic acid, acetic acid and carbon dioxide (CO2). CO2 is
responsible for eye formation and propionic acid results in the typical
nutty flavour of Swiss-type cheese. There have been a few reports of
interactions between a small number of LAB and PAB but the
compounds involved have not been identified. A better
understanding of this phenomenon is necessary to select strains of
PAB for cheesemaking and improve the quality of hard cheeses.
Cheese cannot be used for such a study because of its complexity and
the length of time it is ripened. Hence, a simple whey-based model
developed by Piveteau et al (1995) was successfully used to study the
interactions between LAB and PAB. In this procedure, the LAB were
grown overnight in milk and the whey was collected by centrifugation.
After neutralisation and filter-sterilisation, the growth of strains of PAB
in this whey and in a control whey produced from the same milk by
acidification with lactic acid were compared.
The objectives of this study were to refine the model of Piveteau et al
(1995) to study the interactions between LAB and PAB and to
determine the nature of the stimulant(s) produced by the LAB. * Thirty-two combinations of different commercial strains of PAB and
LAB were evaluated in a modified whey model. None showed any
inhibition and all showed some degree of stimulation but the extent of the stimulation depended on the particular pair of PAB and LAB
used.
* An inhibitor of PAB was found in milk, which prevented the growth
of PAB from low (105 cfu/ml) but not from high inocula (107 cfu/ml).
The inhibitor was heat stable (to autoclaving for 15 min), of low
molecular mass and could be removed by pre-growth of some but not
all starter LAB in milk.
* Growth of P. freudenreichii DPC 3801 in control whey was
stimulated by peptone, tryptone, casein hydrolysed by the crude
proteinase of Lb. helveticus DPC 4571 and by pre-growth of the
lactobacillus in milk, but not by vitamins (riboflavin, thiamine, PABA,
Ca panthothenate, biotin and nicotinic acid) or minerals (MgSO4,
MnCl2, CoCl2 and CuSO4).
* Growth of Lb. helveticus DPC 4571 in milk resulted in significant
increases in peptide and amino acid production but the amino acids
produced did not stimulate the growth of the PAB. Based on these
results it was concluded that the stimulation was due to production of
peptides by the LAB from casein.
* The whey model developed by Piveteau et al (1995) to study the
interactions between PAB and LAB was shown to be reproducible.
Adjustment of the pH of the whey to 5.4 rather than 6.0, incubation
at 24ÂșC rather than 30ÂșC and addition of 1% NaCl, to simulate
cheese ripening conditions allowed growth of all the PAB tested.
* Several chromatographic procedures, including ion-exchange, gel
permeation and reverse-phase, high-pressure liquid chromatography
failed to categorically identify the peptide(s) responsible for the
stimulation of the PAB. In some of these chromatographic systems,the stimulatory activity was shown to be present in several peaks
implying that different peptides were involved.European Unio
The Importance of Hands-on Experience with Telescopes for Students
Proper interpretation and understanding of astronomical data requires good
knowledge of the data acquisition process. The increase in remote observing,
queue observing, and the availability of large archived data products risk
insulating astronomers from the telescope, potentially reducing their
familiarity with the observational techniques crucial in understanding the
data. Learning fundamental observing techniques can be done in at least three
ways: 1) College and university operated observing facilities, 2) Student
involvement in national facilities through competitive proposals, 3) Programs
at national facilities to increase upper-level undergraduate and graduate
student exposure to telescopes. We encourage both national organizations and
universities to include programs and funding aimed at supporting hands-on
experience with telescopes through the three methods mentioned.Comment: "State of the Profession" white paper for the 2010 Astronomy and
Astrophysics Decadal Surve
Astronomy below the survey threshold in the SKA era
Astronomy at or below the 'survey threshold' has expanded significantly since the publication of the original 'Science with the Square Kilometer Array' in 1999 and its update in 2004. The techniques in this regime may be broadly (but far from exclusively) defined as 'confusion' or 'P(D)' analyses (analyses of one-point statistics), and 'stacking', accounting for the flux-density distribution of noise-limited images co-added at the positions of objects detected/isolated in a different waveband. Here we discuss the relevant issues, present some examples of recent analyses, and consider some of the consequences for the design and use of surveys with the SKA and its pathfinders
Radio Jet Feedback and Star Formation in Heavily Obscured Quasars at Redshifts ~0.3-3, I: ALMA Observations
We present ALMA 870 micron (345 GHz) data for 49 high redshift (0.47<z<2.85),
luminous (11.7 < log L(bol) (Lsun) < 14.2) radio-powerful AGN, obtained to
constrain cool dust emission from starbursts concurrent with highly obscured
radiative-mode black hole (BH) accretion in massive galaxies which possess a
small radio jet. The sample was selected from WISE with extremely steep (red)
mid-infrared (MIR) colors and with compact radio emission from NVSS/FIRST.
Twenty-six sources are detected at 870 microns, and we find that the sample has
large mid- to far-infrared luminosity ratios consistent with a dominant and
highly obscured quasar. The rest-frame 3 GHz radio powers are 24.7 < log P3.0
GHz (W/Hz) < 27.3, and all sources are radio-intermediate or radio-loud. BH
mass estimates are 7.7 < log M(BH) (Msun) < 10.2. The rest frame 1-5 um SEDs
are very similar to the "Hot DOGs" (Hot Dust Obscured Galaxies), and steeper
(redder) than almost any other known extragalactic sources. ISM masses
estimated for the ALMA detected sources are 9.9 < log M(ISM) (Msun) < 11.75
assuming a dust temperature of 30K. The cool dust emission is consistent with
star formation rates (SFRs) reaching several thousand Msun/yr, depending on the
assumed dust temperature, however we cannot rule out the alternative that the
AGN powers all the emission in some cases. Our best constrained source has
radiative transfer solutions with ~ equal contributions from an obscured AGN
and a young (10-15 Myr) compact starburst.Comment: 29 pages, 8 figures. To appear in Astrophysical Journal. Update on
Sept 14 to correct the ALMA proposal id. to ADS/JAO.ALMA#2011.0.00397.S and
to add a missing acknowledgemen
Gelatinous Zooplankton Biomass In the Global Oceans: Geographic Variation and Environmental Drivers
Aim
Scientific debate regarding the future trends, and subsequent ecological, biogeochemical and societal impacts, of gelatinous zooplankton (GZ) in a changing ocean is hampered by lack of a global baseline and an understanding of the causes of biogeographic patterns. We address this by using a new global database of GZ records to test hypotheses relating to environmental drivers of biogeographic variation in the multidecadal baseline of epipelagic GZ biomass in the world\u27s oceans. Location
Global oceans. Methods
Over 476,000 global GZ data and metadata items were assembled from a variety of published and unpublished sources. From this, a total of 91,765 quantitative abundance data items from 1934 to 2011 were converted to carbon biomass using published biometric equations and species-specific average sizes. Total GZ, Cnidaria, Ctenophora and Chordata (Thaliacea) biomass was mapped into 5° grid cells and environmental drivers of geographic variation were tested using spatial linear models. Results
We present JeDI (the Jellyfish Database Initiative), a publically accessible database available at http://jedi.nceas.ucsb.edu. We show that: (1) GZ are present throughout the world\u27s oceans; (2) the global geometric mean and standard deviation of total gelatinous biomass is 0.53â±â16.16âmg C mâ3, corresponding to a global biomass of 38.3 Tg C in the mixed layer of the ocean; (3) biomass of all gelatinous phyla is greatest in the subtropical and boreal Northern Hemisphere; and (4) within the North Atlantic, dissolved oxygen, apparent oxygen utilization and sea surface temperature are the principal drivers of biomass distribution. Main conclusions
JeDI is a unique global dataset of GZ taxa which will provide a benchmark against which future observations can be compared and shifting baselines assessed. The presence of GZ throughout the world\u27s oceans and across the complete global spectrum of environmental variables indicates that evolution has delivered a range of species able to adapt to all available ecological niches