Helmholtz Zentrum für Infektionsforschung Repository
Not a member yet
4806 research outputs found
Sort by
NEUERE ENTWICKLUNGEN ZUM EINSATZ VON ENZYMEN BEI DER LEBENSMITTELPRODUKTION
No full textA review is given about the present situation of enzyme application
as to food and nutrition. In this connection emphasis is put on present
position and knowledge /a/ as well as actual impacts of development
/b/ in this field. As to the first topic the following aspects
are discussed: Soluble enzymes, immobilized systems, phenotypic and
genotypic optimization. With regard to modern fields of research the
lecture deals with proteinases, starch modifying enzymes, pectinolytic
enzymes, cellulases/glucanases, lipases and enzymes or enzymatically
effective systems resp. for flavour generation
Biosensors for On-Line Monitoring of the Waterways and for Sample Taking Aimed at Relieving Disturbances
No full textOrganismic and suborganismic testing methods are well suited as biological warning
systems (biosensors) which build a sensitive system used in screening for hazardous
substances.
Although chemo-physical testing methods can never detect and identify all polluting
chemicals in the environment to the fullest extent, biological early warning systems
make it possible to monitor dangerous substances or groups of substances in waterways.
Electrodes made up of cyanobacteria, i.e. Synechococcus, for immediate detection of
acute toxic effects, are used as a biological early warning system for recognizing damage
to the waterways.
The so-called “cyanobacterial electrodes” are graphite electrodes (see Figure 1)
which have cyanobacteria, i.e. Synechococcus, affixed to them. The measurements of the
photosynthetic electron transport system, PET, under alternating light - dark conditions,
are conducted in a flow-through cell against reference electrodes (Ag/AgCl).. A mediator
(Fe II / Fe III) makes the flow of current possible by becoming reduced by these
bacteria and then reoxidized at the working electrode. The time which the electrode takes
to react is about two minutes, and a multiple confirmed result is available after ten
minutes. The detection limits for the individual substances have been set according to
the results obtained up to present at less than 10 Ug per litre for atrazine and at 100 ug
per litre for linuron (see Table 1)
WIRTSCHAFTLICHE ASPEKTE : Einführung
No full textIn dem einleitenden Vortrag von Herrn Hepner wurde die Entwicklung der Wirtschaftlichkeit von SCP
in Bezug der Kostenentwicklung der Rohstoffe: Kohlenwasserstoffe, Methanol und Athanolinnerhalb
der letzten zehn Jahre umfassend dargelegt. Der große Konkurrent zu SCP ist und wird auch
in Zukunft vor allem Soja sein. Sehr wahrscheinlich wird Soja preislich stabil bleiben ‚damit zunehmender
Konkurrenz unter den Hauptproduzenten USA, Brasilien und Argentinien zurechnen
ist. Unter diesen Aspekten kam Herr Hepner zu der Prognose, daß als Ausgangsstoffe für die SCPProduktion
bevorzugt Substrate wie Sulfitablauge oder Molke in Frage kommen, SCP auf der Basis
von Methanol wird, insbesondere nach weiterer Veredelung, als Nahrungsmittelzusatz, einen gewissen
Markt einnehmen
DIE PREISWURDIGKEIT VON SCP, DARGESTELLT ANHAND VON LINEAREN RECHENBEISPIELEN
No full textSummary
Using the three types of feed designated "Broiler fattening
feed", "Trout feed", and "Milk replacer for calves", an
attempt has been made to answer the question of the costeffectiveness
of SCP with the aid of linear programming (LP).
It was shown that, under certain conditions, at a price of
DM 120.00/100 kg of SCP good possibilities for use arise.
These possibilities are greatly dependent on the particular
price for soybean meal and on the planned area. of use. For
this reason, two soybean meal prices, namely DM 40.00 and
DM 70.00/100 kg, were used as models for the basis of the
calculations.
At a price of DM 40.00/100 kg,* a pricing of DM 70.00 to
120.00/100 kg results for SCP, and this pricing rises
correspondingly to the order of magnitude of DM 119.00 to
131.80/100 kg if a high protein-price level exists. Under
special conditions, a pricing was even found of DM 235.00/
100 kg for SCP.
It can therefore be determined that SCP represents an
interesting and high-grade protein component which under
certain conditions offers good possibilities for use in
animal nutrition, whereby its use outside the European
Community must be evaluated as even more favorable because
a wide price difference between grain (sources of energy)
and oil plant meals (sources of protein) exists there. But
ultimately there is always a dependence on the particular
price relationships
ZUM MECHANISMUS DER PROTEINADSORPTION AN HYDROPHOBEN GELOBERFLÄCHEN
No full textAlkylreste mit einer Kettenlänge von 1-4 C-Atomen wurden mit Hilfe der BrCN-Methode
kovalent an einem hydrophilen Trägergel (Agarose, Sepharose 4B [Pharmacia, Uppsala)
immobilisiert. Die immobilisierten Alkylreste bilden auf der Geloberfläche ein zweidimensionales
Bindungsstellengitter, an dem Proteine adsorbiert werden können. Die Bindung
von Proteinen ist komplex und verläuft nicht nach den Gesetzmäßigkeiten einer
Langmuir-Isotherme. Besondere Merkmale der Proteinadsorption an solchen Geloberflächen
sind Kooperativität und Hysterese. Eine positive Kooperativität der Adsorption wird in
Abhängigkeit von der Oberflächenkonzentration der immobilisierten Alkylreste beobachtet.
Eine negative Kooperativität der Adsorption findet man in Abhängigkeit von der Proteinkonzentration.
Die Hysterese ist ein Ausdruck der thermodynamischen Irreversibilität
der Adsorption und des Fehlens eines Gleichgewichtsüberganges
REAKTIVEXTRAKTION
No full textNach einer Übersichtsdarstellung der Chemie reaktiver Extraktionsprozesse werden
neue Ergebnisse auf dem Gebiet der Berechnung von Reaktivextraktionsverteilungsgleichgewichten
sowie der Verfahrensauslegung von Box-Mixer-Settlern aufzeigt.
Aus Platzgründen konzentriere ich mich ganz auf die Darstellung der Reaktivextraktion
ionischer Spezies (vornehmlich Metallionen)
CELLULOSE DECOMPOSING MYXOBACTERIA
No full text200 strains belonging to the order Myxobacterales were isolated from
farm yard manure, compost, liquid manure and soil. These strains were
tested for their ability to utilize cellulose. Most of the strains decomposed
the cellulose. Myxobacteria decomposed 9-82 per cent of cellulose.
They are mesophilic aerobic microorganisms. The highest degree of decomposition
of cellulose by the different myxobacteria depends on the form of
nitrogen in the substrate. The course of decomposition of cellulose is
affected by the temperature.The highest degree of decomposition was at
28°C. The extreme temperatures (below 8°C, above 42°C) are not convenient
for decomposition. The course of decomposition is affected by the moisture,
too. Fairly good decomposition proceeded at 21 per cent moisture
level. Moisture within 15-20 per cents accelerated the decomposition of
cellulose.
In the evaluation of the coenoses of cellulolytic microorgansms, myxobacteria
are widely distributed microorganisms not only in farm yard
manure but in the soil as well. Myxobacteria belong to typical soil flora
and participate quite actively in the decomposition of cellulose in
the soil. They are specially predominant cellulolytic microflora in
manured soil. Therefore the biological activity of fertilized soil can
be fairly estimated by the cellulolytic test
AMPLIFICIATION AND SWITCHING BY ENZYMES IN BIOSENSORS
No full textBiospecific electrodes based on the membrane technology (first generation
of biosensors) for nine metabolites (glucose, lactose, maltose,
lactate, pyruvate, urea, uric acid, glutamate, and phosphate) and
for the determination of six enzyme activities (o-amylase, lactate
dehydrogenase, pyruvate kinase, creatine kinase, alanine aminopeptidase,
and choline esterase) have been brought into the clinical
laboratory by our group. These sensors contain a dialysis membrane
and up to three sequentially acting enzymes. For mono-enzyme electrodes
200 - 300 samples per hour, a functional stability of 5,000 -
10,000 samples per membrane and a lower limit of detection of 1 zum
have been achieved.
An increase of sensitivity up to the lower nanomolar range has been
achieved by analyte recycling enzyme systems. In addition to the couples
lactate/pyruvate, glucose/gluconolactone, NAD*/NADH, ADP/ATP, in
the enzyme system laccase/cytochrome bs benzoquinone/hydroquinone
have been amplified. This sensor exhibits a cosubstrate-dependent
thresholdlike sensitivity. Cofactor-dependent anti-interference
layers, e.g., hexokinase or glucose dehydrogenase, represent another
type of enzymatic switches. Their selectivity may be changed by
turning on the eliminating enzyme
BIOREACTOR SYSTEM FOR CLINICAL ANALYSIS
No full textThe usefulness of enzymes as the reagents for clinical analysis has
been well documented. The enzymes can be used not only in the form of
solution but also in the form of immobilized enzyme reactor. A columntype
reactor can be readily applied to any continuous flow analytic
system. Combined use of flow injection and chemiluminometric detection
makes it possible to minimize the sample volume and the analysis time.
Two or three different kinds of immobilized enzymes can be aligned in
a minicolumn reactor so that the sequential enzymatic reactions be
carried out from upstream to down stream without noticeable backward
flow of the solutes. Typical examples of the applicability of such
bioreactors to clinical analysis are presented. The determination of
serum creatinine by sequentially aligned immobilized glutamate dehydrogenase
and creatinine deiminase is illustrated. A novel chemiluminometric
determination of ammonia by successive passage of the analyte
through immobilized urease, glutamate dehydrogenase, and glutamate
oxidase is also described
MATHEMATICAL MODELING OF AMPEROMETRIC ENZYME ELECTRODES
No full textThe advantages of computer assisted enzyme electrode design are demonstrated
for the case of electrodes with cycling reactions.
1. Introduction
The number of really existing amperometric enzyme electrodes is increasing.
The arrangements become more and more complicated:
- several enzymes are combined to enzyme systems
— non-stationary operational modes are used
— enzymes with non-linear kinetics are applied
The designer of new enzyme electrodes can be much supported by making available
suitable mathematical models:
- calculation of all concentration profiles involved in the enzyme membrane
(understanding of the basic principles)
— prediction of the dynamic behaviour of the sensor, e.g. current/time behaviour,
response time, linear measuring range.
- optimizing of the sensor design (cost saving use of enzymes, achievement of
given device parameters, use of commercial enzymes).
This aim can be realized by a user-friendly software package which operates
in the laboratory on a personal computer. The corresponding mathematical fundamentals
are available:
— one-dimensional reaction/diffusion systems are proved to be good
- linear models have been investigated extensively, numerous explicit formulae
have been derived
— numerical methods and the tools for software development (compiler, libraries,
graphics) are international standard