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51.
52.
Ashby RD Solaiman DK Foglia TA 《Journal of industrial microbiology & biotechnology》2002,28(3):147-153
Pseudomonas oleovorans NRRL B-778 accumulated mixtures of poly-3-hydroxybutyrate (PHB) and medium-chain-length poly(hydroxyalkanoates) (mcl-PHAs) when grown on glucose, octanoic acid or oleic acid, whereas growth on nonanoic acid or undecanoic acid resulted in
copolymers of poly-3-hydroxybutyrate-co-3-hydroxyvalerate (PHB-co-HV). Acetone fractionation verified the presence of PHB/mcl-PHA mixtures. The acetone-insoluble (AIS) fractions of the polymers derived from glucose (PHA-glucose), octanoic acid (PHA-octanoic)
and oleic acid (PHA-oleic) were exclusively PHB while the acetone-soluble (AS) fractions contained mcl-PHA composed of differing ratios of 3-hydroxy-acid monomer units, which ranged in chain length from 6 to 14 carbon atoms.
In contrast, both the AIS and AS fractions from the polymers derived from nonanoic acid (PHA-nonanoic) and undecanoic acid
(PHA-undecanoic) were composed of comparable ratios of 3-hydroxybutyrate (3HB) and 3-hydroxyvalerate (3HV). The unfractionated
PHA-glucose, PHA-octanoic and PHA-oleic polymers had melting temperatures (T
m) between 177 and 179°C, enthalpies of fusion (ΔH
f) of 20 cal/g and glass transition temperatures (T
g) of 3–4°C. This was due to the large PHB content in the polymer mixtures. On the other hand, the PHA-nonanoic and PHA-undecanoic
polymers had thermal properties that supported their copolymer nature. In both cases, the T
m values were 161°C, ΔH
f values were 7cal/g and T
g values were −3°C. Journal of Industrial Microbiology & Biotechnology (2002) 28, 147–153 DOI: 10.1038/sj/jim/7000231
Received 30 July 2001/ Accepted in revised form 04 November 2001 相似文献
53.
The mycotoxin aflatoxin M1 (AfM1) is a serious food safety hazard for which the European Commission has already established a maximum permissible level of 0.05 μg/kg AfM1 in milk and products thereof. For control analysis laboratories are increasingly asked to submit full uncertainties of their analytical results.The evaluation of measurement uncertainties of an analytical method for the determination of AfM1 in milk and milk powder on the basis of ‘in-house’ validation data in compliance with the ‘Guide to the Expression of Uncertainty in Measurement (GUM)’ [1] and the ‘EURACHEM Guide’ [2] is described. A similar approach will be used to assess the performance of methods employed by laboratories participating in the certification of reference materials for AfM1 in milk powder. 相似文献
54.
1. Many fish stocks have declined, because of overharvesting, habitat destruction and introduced species. Despite efforts to rehabilitate some of these stocks, not all are responding or are recovering only slowly. 2. In freshwater systems, introduced crayfish are often problematic, and it has been suggested that their egg predation could reduce recruitment in depleted stocks of native fish. 3. Here, we report the results of a field experiment, using experimental cages, on the extent of predation on eggs of great Arctic charr (Salvelinus umbla) in Lake Vättern, Europe’s fifth largest lake. Here, the great Arctic charr has declined dramatically and is listed as critically endangered. 4. We were able to partition the total loss rate of eggs into background mortality, predation by introduced signal crayfish (Pacifastacus leniusculus) and predation by native fish. The mortality rate of charr eggs because of crayfish was estimated at more than five times that because of native fish. Of the total loss of eggs, 80% is believed to be caused by crayfish and 14% by fish, with 6% being natural background mortality. 5. In a worst case scenario, our data infer that only 25% of the original number of eggs would survive, compared with 75% in the absence of crayfish. This could impair recovery of the stock of the endangered great Arctic charr in Lake Vättern. 6. Contrary to earlier claims that crayfish predation on eggs of great Arctic charr is insignificant, our results indicate that crayfish predation may exceed fish predation and suggest that the abundance of signal crayfish on the spawning sites of great Arctic charr should be managed. 相似文献
55.
56.
Cytochrome c oxidase vesicles were used to show that, under appropriate experimental conditions: (1) no net deprotonation of the vesicular membrane or of the incorporated enzyme occurs during the oxidation of ferrocytochrome c; (2) the pH equilibration kinetics of a respiration-induced pH gradient across the bilayer are a simple function of the ohmic proton-conductance properties of the membrane; (3) a fairly constant stoichiometry (0.8-0.7) of the numbers of protons pumped per molecule of ferrocytochrome c oxidized, i.e. the H+/e- ratio, over a wide range of dioxygen molecules reduced (1-12) is observed. 相似文献
57.
Abstract A multidisciplinary field study investigating the fate and transport of petroleum hydrocarbons commonly associated with jet-fuel contamination is currently underway at Columbus Air Force Base (AFB), Mississippi. Sixty sediment cores from 12 boreholes were recovered from the study aquifer. The goal of this initial sampling was to characterize the potential microbial activity using 14C-labeled substrates, as well as the presence, abundance, and distribution of specific hydrocarbon degrading genotypes using DNA:DNA hybridization. Enumeration of total microbial abundance using a 16S rDNA universal oligonucleotide probe was compared to traditional enumeration methods. Total culturable populations determined by spread plate analysis ranged from a low of 10(4) to more than 10(6) organisms per gram sediment. Microbial abundance estimated by DNA hybridization studies with 16S rDNA genes ranged from 10(7) to 10(8) organisms per gram sediment. Molecular analysis of aquifer samples using DNA probes targeting genes encoding the degradative enzymes alkane hydroxylase (alkB), catechol 2,3-dioxygenase (nahH), naphthalene dioxygenase (nahA), toluene dioxygenase (todC1C2), toluene monooxygenase (tomA), and xylene monooxygenase (xylA), as well as two probes measuring methanogenic microorganisms, codh (carbon monoxide dehydrogenase) and mcr (methyl coenzyme reductase), revealed that each target gene sequence was present in nearly all 60 samples. The presence of organisms demonstrating the phenotype to degrade BTEX and naphthalene was further supported using mineralization assays with 14C-labeled benzene, toluene, naphthalene, and phenanthrene. Minimal activity occurred during the first 24 hours. After a period of 5-7 days, greater than 40% of the target compounds were mineralized in aquifer sediments. 相似文献
58.
The acidic glycolipid fraction (AF) of the porcine, parasitic nematode,
Ascaris suum , consisted of two subfractions. The major component AF II
reacted with orcinol-sulfuric acid and molybdate, while the minor component
AF I gave a positive reaction with azure-A, a cationic dye specific for
sulfatides. Sugar constituent analysis, methanolysis, methylation analysis,
matrix-assisted laser desorption/ionization time- of-flight mass
spectrometry, liquid secondary-ion mass spectrometry, and gas-liquid
chromatography/mass spectrometry specified AF II to be an unusual
phosphoinositolglycosphingolipid (Galalpha1-Ins-P-1ceramide) and the minor
component AF I to be a 3-sulfogalactosylcerebroside (HSO3-
3Galss1-1ceramide). The ceramide moiety of both components consisted of
lignoceric (C24:0) and cerebronic (C24h:0) acids and mainly C17 iso-
branched sphingosine. Immunohistochemical localization studies of the
glycolipid-bound antigenic determinants with a polyclonal antiserum against
AF II and an anti-sulfatide monoclonal antibody against AF I revealed the
presence of the AF II-epitope in the intestine, whereas the AF I-epitope
was found in the hypodermis, contractile zone of somatic muscle cells and
the external musculature of the uterus. To our knowledge, this is the first
report of the presence of a sulfatide in an invertebrate.
相似文献
59.
60.
RD Calixto R Verlengia AH Crisp TB Carvalho MD Crepaldi AA Pereira AK Yamada GR da Mota CR Lopes 《Biology of sport / Institute of Sport》2014,31(4):289-294
This study aimed to compare the effects of different velocities of eccentric muscle actions on acute blood lactate and serum growth hormone (GH) concentrations following free weight bench press exercises performed by resistance-trained men. Sixteen healthy men were divided into two groups: slow eccentric velocity (SEV; n = 8) and fast eccentric velocity (FEV; n = 8). Both groups performed four sets of eight eccentric repetitions at an intensity of 70% of their one repetition maximum eccentric (1RMecc) test, with 2-minute rest intervals between sets. The eccentric velocity was controlled to 3 seconds per range of motion for SEV and 0.5 seconds for the FEV group. There was a significant difference (P < 0.001) in the kinetics of blood lactate removal (at 3, 6, 9, 15, and 20 min) and higher mean values for peak blood lactate (P = 0.001) for the SEV group (9.1 ± 0.5 mM) compared to the FEV group (6.1 ± 0.4 mM). Additionally, serum GH concentrations were significantly higher (P < 0.001) at 15 minutes after bench press exercise in the SEV group (1.7 ± 0.6 ng · mL−1) relative to the FEV group (0.1 ± 0.0 ng · mL−1). In conclusion, the velocity of eccentric muscle action influences acute responses following bench press exercises performed by resistance-trained men using a slow velocity resulting in a greater metabolic stress and hormone response. 相似文献