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FLOW SYSTEMS FOR THE SIMULTANEOUS CONCENTRATION CONTROL OF DIFFERENT SUBSTRATES DURING FERMENTATION
No full textBiosensors have successfully been used for the specific detection and
determination of many substances in clinical chemistry, food analysis
and environmental control. A more recent field for their possible
application is fermentation control, where continuous measuring of
' many substances over longer periods is needed. The actual bottle neck
i in corresponding process controls is the lack of an automated
determination of substrates, products, coenzymes and enzyme activities,
because so far in fermentors only a few parameters can continuously be
measured
FIBER OPTIC DETECTION OF PESTICIDES IN DRINKING WATER
No full textThe article describes a method for remotely sensing pesticides in contaminated water via fiber
optical light guides. It is based on the capability of pesticides to inhibit the formation of a
blue dye from a red enzyme substrate. The device has the advantages of high sensitivity, fully
battery-powered operation, and true remote sensing in that no power supply is required at the
sensingsite
An in situ Fermenter Probe for Bakers Y east Propagation Monitoring
No full textA fermenter probe was developed based on the immobilisation of glucose
oxidase at an amperometric mediated graphite electrode. The response
characteristics of the probe made it readily applicable to continuous
monitoring of glucose concentration during bakers yeast propagation
ALCOHOL DETERMINATION BY MODIFIED CARBON PASTE ELECTRODES
No full textThe basis of this alcohol sensor is the oxidation of ethanol by NAD*
with alcohol dehydrogenase as the catalyzing enzyme. The NADH formed is
detected electrochemically at 700 mV versus a Ag/AgCl-electrode. The
electrode used is a carbon paste electrode with the enzyme and the
cofactor mixed into the paste. The sensor can be used up to concentrations
of approximately 0.15 Mol/1 (i. e. 1 Vol%), with a response time
of 15 s and a stability of at least 7 days
AN ION SENSITIVE FIELD EFFECT TRANSISTOR FOR BIOSENSOR APPLICATION
No full textAs on the one handa field effect transistor (FET) is a widespreadelectronic device
for a potentiometric measuring of electrical phenomena, on the other hand change
of dipole moments or accumulation of net charge occur as a consequence of a
biological reaction, the combination of an ion sensitive field effect transistor (ISFET)
with a biological layer, the so-called Bio-FET, is an excellent device for
measuring concentrations of biological substances in a sample solution.
The ISFET,fabricated by the semiconductor technology with low fabrication costs,
offers the possibility of integrating signal processing together with the FET-sensor.
Principle of function, layout of the sensor chip, integrated multi sensor array, experimental
results are the topics treatedin this paper
ENZYME AND IMMUNE ELECTRODES FOR THE CLINICAL LABORATORY
No full textDifferent variants of glucose oxidase electrodes and equipment for it
have been successfully used for years in health institutions in the GDR.
In addition to glucose in blood, urine glucose can also be measured,
where there is a similarity to the hexokinase method. For this however,
instead of measuring the maximum transformation velocity of the H205
oxidation flow, the oxygen uptake must be determined. The possibility of
carrying out an enzyme electrochemical dry test is demonstrated using a
simple device, which serves to measure glucose with enzyme films.
In spite of its good analytical quality, an enzyme-free amperometric
measurement of uric acid has only attained little practical use. The
reasons for this are drug interactions. Studies on analyte diffusion
through the membrane to the electrode demonstrate this. Enzyme
activities from ‘380i: 50¢nM oh sat <i emae in the uricase membrane yield
electrodes with good measuring characteristics.
Catalase electrodes make a simple performance of the indicator reaction
in enzyme immuno-assays possible. A distinct improvement of the
analytical quality could not be observed when compared to the photometer
method
SOME NEW ENZYME ELECTRODES
No full textElectron transfer reactions of redox proteins are studied using
electrochemical methods. It is emphasised that the electron transfer occurs
without mediation. For many redox proteins, the rate of the electron transfer
depends critically on the presence in solution of positively-charged metal ions.
In instances where direct electron transfer is very slow, as is the case at
present with many potentially useful enzymes, indirect mediated electron transfer
is used. Of particular value as mediators are ferrocenes, not only because they
take part in rapid, reversible electrochemistry but because of the wide variety of
compounds that can be prepared. Their use in a variety of sensors is illustrated
in electrochemical assays for glucose and cholesterol and their application in
electrochemical immunoassays is illustrated by the analysis of the drug,
lidocaine
IMPLANTABLE GLUCOSE SENSOR - PROBLEMS AWAITING SOLUTIONS FOR LONG-TERM CLINICAL APPLICATION
No full textWe developed an indwelling, exchangeable and disposable glucose
sensor. For preserving excellent in vivo characteristics and extending
sensor longevity, the most crucial points are the elegant membrane
design and the software backup system. We have developed a band path
filter, which was effective in eliminating several types of electrical
noises evoked by muscle works or electrical disturbances. The new
glucose sensor covered by alginate-polylysine-alginate membrane as a
biocompatible one could preserve the sensor activity for 14 days after
implantation in subcutaneous tissue of normal dogs.
These data indicated that further improvements in membrane design
might augment the long-term clinical applicability of glucose sensor
Title - Foreword - Contents - List of Authors
No full textThe two bacterial genera, Cytophaga and Flavobacterium, account for many of the
yellow or orange pigmented, gram-negative bacteria which we isolate from natural and
man-made environments. However, their taxonomy is far from being clear. This is very
unsatisfactory, particularly as many of these bacteria are of considerable practical
importance, appearing quite regularly in the clinical laboratory, or playing a role
as spoilage organisms in the food industry, as fish-pathogens, or as producers of interesting
enzymes and antibiotics. Last but not least, enormous populations of these
organisms live in soil, freshwater, and marine environments, and are undoubtedly
greatly involved in the degradation and turnover of organic substrates in nature, as
well as in sewage plants.
Both "genera" comprise rod-shaped, heterotrophic, primarily aerobic bacteria,
which, in the case of the cytophagas move by gliding, while the flavobacteria are
either immotile or flagellated. As a result of the research of the past 15 years we
can today be sure that both groups are taxonomically heterogeneous. Somewhat unexpectedly,
observations came to the light which suggested connections, perhaps even
relatively close ones, between some of the flavobacteria with a low DNA base ratio
(30 to 40 mol % GtC) and respective Cytophaga-like bacteria (CLB). This meeting has
been organized by us, together with Dr. D. Claus from the DSM (German Collection of
Microorganisms) in Gdttingen to discuss these new developments. Some of the more impressive
data which would indicate a relationship between flavobacteria and CLB are
presented in this volume, e.g. studies on the distribution among these organisms of
lipoquinones, hydroxy fatty acids, and flexirubin-type pigments. Reports on unusual
cellular constituents, like sphingolipids or sulfonolipids, in some of these bacteria
should stimulate investigation into the occurrence of such compounds in other representatives
of this group and might provide valuable additional indications of a relationship.
Of course, further problems still remain to be solved. Thus, it is not yet apparent
how the new genera, Cytophaga and Flavobacterium, should be delimitated and defined,
nor how to proceed with the remaining organisms, e.g. the "flavobacteria" with
a high G+C content (60 to 70 mol %). As can be seen from the contributions of this
symposium, lively discussions ‘take place about such questions, but there is neither
universal agreement yet, nor are there always sufficient available data to enable the
taxonomic problems to be dealt with competently. There are actually large areas in
the taxonomy of flavobacteria and CLB, where we are still only at the start. Modern
taxonomic methods, like those offered by molecular biology, or the chemosystematic
approach, as applied more recently to this difficult group of bacteria, promise progress
in the near future. It is our opinion that this symposium has provided a good
survey of the state of the taxonomy of flavobacteria and CLB, and we hope that it
will stimulate further research.
We should like to take the opportunity to thank all those persons who helped to
make this symposium possible. The directors of the GBF, Prof. Dr. K. Kieslich and
Dr. H. Zeitträger, were in favor of our enterprise from the very beginning, and allowed
us to use the lecture room as well as the facilities of the institute. They
also gave us essential financial support. R. Radloff solved most of the organizational
problems, and Karin Rahn typed many letters in connection with the symposium and had
much work with the articles for this proceedings volume. Dr. J.H. Walsdorff gave valuable
assistance in compiling and editing this volume
BIOSENSORS WITH FLUORIDE ION SENSITIVE FIELD EFFECT TRANSISTORS
No full textEnzyme field effect transistors for Qlucose and lactate were
developed by coupling a new transducer type, the fluoride ion
sensitive FET, with the peroxidase-catalyzed reaction liberating
fluoride ions from organo-fluoro compounds in the presence of
hydrogen peroxide “which was produced in coupled oxidase
reactions. Glucose oxidase or lactate oxidase and peroxidase
were coimmobilized with human serum albumin or polyurethan at a
multigate pF-FET. 4-fluoroaniline and pentafluorophenol were used
as organo-fluoro compounds. The main functional parameters are
given