Helmholtz Zentrum für Infektionsforschung Repository
Not a member yet
4806 research outputs found
Sort by
Ta205-pH-ISFET: A BASIC STRUCTURAL ELEMENT FOR BIOSENSOR APPLICATIONS
No full textThe wide range of ion-sensitive layers, be they inorganic or organic, that can
be employed for the use with ion-sensitive field-effect transistors (ISFETs) ,
brings to mind the production of a BASIC STRUCTURAL ELEMENT (1). After
adjusting to the requirements of MOS-technology, one produces ISFETs containing
all layers up to the last ion-sensitive layer; here the basic structural
element may already be sensitive to one type of ion as is the case with the
pH-sensitive Tag0s5-layer. Then, as a final step in the process, the special
sensitive layer e.g. containing organic ion exchangers or enzymes can be
applied by the ultimate user himself. Moreover this procedure allows older,
used layers which no longer respond reliably and reproducably to be removed and
replaced by a fresh layer. Of course this procedure presupposes a thorough
knowledge of the properties of the layer systems, as regards their stability and
reproducibility
DEVELOPMENT OF BIOSENSORS USING OPTICAL FIBERS
No full textFiber optic biosensing probes consist of an immobilized biocatalytic
layer at the distil tip of an optical fiber device. In the presence
of the bioanalyte, the biocatalyst generates an optical signal which
is measured and related to the bioanalyte concentration. Three new
classes of fiber optic biosensors are presented. The first class is
based on the immobilization of a deaminating enzyme at the tip of an
fiber optic ammonia sensor. The first fiber optic urea sensor has
been successfully demonstrated by immobilizing urease at the tip of an
optimized fiber optic ammonia sensor. The second type of fiber optic
biosensor is based on the immobilization of a dehydrogenase enzyme and
the fluorometric detection of reduced nicotinamide adenine
dinucleotide (NADH) at the distil tip of an optical fiber bundle. The
feasibility of this NADH-based biosensor strategy has been
successfully demonstrated with biosensors for lactate and pyruvate.
Finally, a novel biosensor arrangement is introduced where the
biocatalyst is separated from the sample solution by a gas-permeable
membrane. This "internal enzyme" approach has been demonstrated with
an ethanol sensor in which alcohol dehydrogenase is employed as the
enzyme and the production of NADH is detected fluorometrically.
Relative merits and future prospects for these three types of fiber
optic biosensors are discussed
THE USE OF AMINOPEPTIDASES IN THE FOOD INDUSTRY
No full textThis paper introduces a new group of industrial enzymes with
application in the food industry: the aminopeptidases.
Endoproteolytic enzymes have been used in the food industry for
many years. One of the main drawbacks of endoprotease enzymes is
their capacity to produce bitter hydrolysates. The bitterness is
derived from peptides rich in hydrophobic amino acids. This is a
general problem which the industry has faced for many years and
which has severely limited the use of protein hydrolysates in food
and health care products. Traditional methods of bitterness
control include masking, removal of bitter peptides or prevention
by limiting the degree of hydrolysis. However, these methods have
a very limited effectiveness.
The use of a newly commercialised group of enzymes, the
aminopeptidases, in conjunction with specific endoproteases
completely removes the bitterness normally associated with protein
hydrolysis and allows many developments of significant industrial
potential. The aminopeptidases function is to cleave single or
pairs of amino acids from the N-terminal end of polypeptide
chains, which prevents the formation of bitter peptides. This can
result in greatly improved organoleptic properties coupled with
improved nutritional characteristics.
The high cost of animal proteins has led to the enzymatic
treatment of plant and dairy proteins in an attempt to increase
their value by changing functional characteristics and improving
organoleptic and nutritional properties. IBT has developed a
number of enzyme preparations containing aminopeptidases and
proteases which allow the hydrolysis of proteins to be controlled
within a DH range of between 1 and 25%, without producing any
bitterness. Enzyme blends are tailored for a wide variety of
protein sources including casein, whey, soy and gluten. ‚In
addition, aminopeptidase blends are available for debittering
protein hydrolysates and cheese products.
Imperial Biotechnology manufactures a range of aminopeptidases
from food grade bacterial and fungal sources. We are now
providing enzyme blends for the modification of functional
properties such as emulsification, gelling and foaming, production
of nutritional hydrolysates and in the accelerated ripening of
hard cheeses
ENZYMATISCHE KONSERVIERUNG VON RHABARBERKONFITÜRE
No full textDas Einkochen von Früchten mit Zucker zu Konfitüre ist eines der ältesten Verfahren
der Menschheit, Lebensmittel durch Wasserentzug haltbar zu machen. Unter Zusatz von
höchstens 55% Zucker (Saccharose), Obst- oder Mischpektinextrakt, Obstgeliersaft,
Stärkesirup, Citronen-, Wein- oder Milchsäure sowie Fruchtrohsaft, wird ein streichfähiges Erzeugnis hergestellt in einem pH-Bereich von 2,6-3,2.
Die Konfitüre wird während der Verarbeitung und Lagerung ständig dem Angriff des
Sauerstoffs der Luft ausgesetzt. Dies hat zur Folge, daß das Produkt chemischen und
biochemischen sowie mikrobiellen Veränderungen ausgesetzt ists/2/
Glucose Oxidase wird in der Lebensmittelindustrie primär angewandt, um die Lebensmittel vor Farb- und Aromaveränderungen während der Herstellung und Lagerung zu
schützen. Das Enzymsystem, das Glucose Oxidase und Katalase enthält, führt die
Oxidation von D-Glucose zu Gluconsäure bei Anwesenheit von molekularem Sauerstoff
durch. Mittels Glucose Oxidase/Katalase-Präparationen werden die Sauerstoff-Konzentrationen im Kopfraum untersucht und die analogen Qualitätsveränderungen der Konfitüre beobachtet (Farbänderungen)
ENZYMANALYTIK IN DER LEBENSMITTELINDUSTRIE - HEUTE
No full textEnzymes, the catalysts of the living cell, fasten the speed of chemical reactions;
they are highly specific towards their substrates and the reactions catalyzed. These
are the reasons why they are used successfully for analysis.
Enzymatic analysis is the determination of metabolites by means of enzymes
(enzymes used as reagents = chemicals), the determination of enzymatic activities, as
well as the use of enzymes as marker substances for the highly specific
antigen-antibody reaction. Enzymatic methods are superior to chemical methods and
often 'better' than physico-chemical separation techniques where they are often used
as reference methods.
Enzymatic procedures for the analysis of sugars, acids, alcohols and other
substances can be applied to food and non-food samples in form of manual assays as
final value or kinetic methods, with discrete and continuous flow automatic systems,
in form of test strips, simple and highly sophisticated ones, or with immobilized
enzymes. Electrodes and other systems using enzymes are used or under development.
Main fields of application of enzymatic methods are e.g. milk and dairy products,
fruit juice, wine, meat and egg products. Reasons for application are control of
technology, quality-price comparisons, control of raw materials and final products,
as well as governmental control to see whether laws and regulations are observed and
the products are labeled in correct way.
Enzymatic methods are recommended nationally and internationally, they are
published in governmental food manuals and in standards.
The determination of enzymatic activities is also of importance in food analysis,
but there are some problems to be solved, especially to find the ‘best’ test system
to get 'good' results, because it is only possible to get optimal data from optimized
methods and not accurate ones
BESTIMMUNG DER GESAMTSÄURE IN WEINEN UND FRUCHTSÄFTEN MITTELS FLIESS-INJEKTIONS-ANALYSE
No full textTitrimetric acid determination by Flow-Injection Analysis (FIA) is known since 1977,
but up till now it has seldom been used in food analysis. Taking wines and fruit
juices as examples, it will be shown that FIA acid titration is a simple but rapid
and reliable method to determine the total acid content of beverages generally.
Agreement with the reference method is better than + 2%. Up to 30 estimations per
hour are possible with each 100 to 150 1 sample volume
ENZYME IN DER LEBENSMITTELTECHNIK UND LEBENSMITTELBIOTECHNOLOGIE - BEISPIELE AUS DEN USA UND WESTEUROPA
No full textThe use of enzymes in the production and processing of foods goes parallel with the
development of biotechnology. Current applications of enzymes also include their uses in
the production and bioconversion of processing aids and food additives, as well as
utilization during storage, transportation, food analysis and quality control.
The recent interest in food biotechnology and in natural products has led to significant
changes in food processing where more and more conventional operations are being
replaced by enzyme catalyzed processes.
Examples presented include the improvement of food quality via enzymes, production of
plant metabolites and development of new processes.
Within the first category, oxygen scavengers, the role of proteases as alternative to
sulphites, nitrate removal and detoxifying enzymes are being discussed. Production of plant
metabolites centers around immobilization and permeabilization procedures for plant cells
and the role of precursors and elicitors for improvement of yields of secondary
metabolites. Also the function of enzymes in the bioconversion of metabolites and the role
of elicitors in enzyme production is being reviewed.
The development of new processes concentrates on antimicrobial enzymes with main
emphasis on lactoperoxidase and a combined lytic enzyme - pressure treatment process for
the destruction of microorganism. Furthermore the potential of ‘enzymatic peeling’ of foods
is being demonstrated.
Der Einsatz von Enzymen in der Produktion und Verarbeitung von Lebensmitteln geht mit
der Entwicklung der Biotechnologie in der Lebensmitteltechnologie einher. Traditionelle
Produkte wie Bier und Kase sind typische Beispiele der seit etwa 8000 Jahren
hergestellten Lebensmittel biotechnologischer Produktion /2-4/. Der Aufschwung der
Biotechnologie im letzten Jahrzehnt sowie die zunehmende Forderung von Konsumenten
nach "natürlichen" und minimal verarbeiteten Produkten hat zugleich einen Aufschwung des
Einsatzes von Enzymen in der Lebensmitteltechnologie gebracht /5/. Dieser reicht von der
Verwendung von Enzymen bei der Herstellung von Lebensmitteln (z.B. zur
Fruchtsaftgewinnung) über deren Einsatz bei der Verarbeitung und Lagerung (z.B. zur
Reifung oder Sauerstoffentfernung) sowie bei der Produktion und Umwandlung von
Lebensmittelhilfs- und -zusatzstoffen (z.B. Lipasen zur Produktion von Aromen) bis zur
Qualitätskontrolle und Analytik (z.B. Biosensoren, enzymatische Schnelltests). Scott /6/
berichtete vor kurzem, daß 75 % der Zitate, die er in einer Übersicht über spezielle
Enzyme für die Lebensmittelindustrie präsentierte, aus den Jahren 1986 oder später
stammen. Dies weist auf die signifikante Bedeutung von Enzymen in der gegenwärtigen
und zukünftigen Forschung im Bereich der Lebensmittelbiotechnologie hin und beleuchtet
das große Potential, das sich für den Einsatz von Enzymen in der Lebensmitteltechnologie
und - biotechnologie bietet.
Der für diese Übersicht zur Verfügung gestellte Platz erlaubt nur, exemplarisch auf einige
Anwendungsgebiete von Enzymen im Bereich der Lebensmitteltechnologie und -
biotechnologie einzugehen
Rechtslage zur Anwendung von Enzymen in Lebensmitteln
No full textEnzyme sind Gegenstand verschiedener lebensmittelrechtlicher Vorschriften. Beispiele sind die Ausnahme vom Zusatzstoffverbot in 3 und Anlage 3
ZZulV sowie die Bedeutung der fermentativen Verfahren für den Begriff natürlicher Aromastoff gemäß $ 1 Abs. 3 AromenV
Three Dimensional Structure Determination of Proteins in PERI
No full textRibonuclease F,, the guanine-specific ribonuclease from
Fusarium moniliforme(1), was crystallized from 2-methyl-2,4-
pentanediol/H,O solution in two different crystal forms,
corresponding to RNase F,-2'GMP complex or the inhibitor-free
enzyme respectively. The molar ratio of 2'GMP/enzyme in the
crystals was determined to be 0.9 by comparing absorbances on UV
spectra. The inhibitor-free crystal belongs to orthorhombic space
group P2,2,2, with unit cell parameters : a=46.6 A, b-56.3 2,
c=31.6 A. The crystal of the complex belongs to hexagonal space
group P6, with cell dimensions ; a=b=40.2, c=120.9. The
inhibitor-free crystal diffracts X-ray very well beyond 1.5 A and
intensity data to 1.8 A were collected with a 4 circle
diffractometer ( Enraf-Nonius CAD4 ) on a sealed tube generator.
Intensity data were also collected from the complex crystal at
2.3 A resolution. RNase F, is by 59 % homologous in sequence with
RNase T, (2) of which three dimensional structure was already
determined with respect to the 2'GMP-enzyme complex(3,4). The
structure analysis of RNase Fy, was carried out about the
inhibitor-free crystal, using molecular replacement technique. We
could trace the whole main chain of RNase F,. Although its entire
conformation including secondary structure is similar to that of
RNase Tj, considerable differences were observed in loop
structures. This may reflect the conformational alteration caused
by binding to 2'GMP (5)
TERTIARY STRUCTURE OF XYLANASE AND ESTIMATION OF ACTIVE SITES BY SITE DIRECTED MUTAGENESIS
No full textThe nucleotide sequence of xylanase gene(xynA) of Bacillus
pumilus IPO, a hyperproducer of xylanase, was determined and
the amino acid sequence was deduced from it. Xylanase is produced
as a preenzyme consisting of the mature enzyme of 201 amino acid
residues and a signal peptide of 27 residues.
Xylanase was analyzed by X-ray crystallography at the level of
2.2 A resolution. It is consisted with two domains, smaller and
larger, between two a crevasse suitable to accept xylan molecule
was observed. The mutant xylanases obtained by site directed
mutagenesis having amino acid alteration; Glu93-Ser93 and
Glul82_Asp182 had no catalytic activity (less than 1/10,000)