Helmholtz Zentrum für Infektionsforschung Repository
Not a member yet
4806 research outputs found
Sort by
LYSOZYM ZUR VERMEIDUNG DER SPATBLAHUNG IN KASE
No full textMilk for cheese manufacture is naturally contaminated with spores,
for instance with those of Clostridium tyrobutyricum, especially
during silage feeding of dairy cattle. In cheese, these bacteria
produce the "late blowing" defect during ripening and impair the
quality to unacceptability. Since nitrate as an preservative is to
be replaced for as it may give rise to the formation of nitrosamines, hen egg lysozyme could be able to take its position. The
estimation of the necessary amount of lysozyme, however, is difficult since a suspension of Micrococcus lysodeicticus cells is to be
used as a substrate to measure its activity in photometrical
reading.
The Federation Internationale de Pharmacie has given a definition of
activity for hen egg lysozyme and offers standard lysozyme to overcome this problem. On short basis, a general definition of the
empirically estimated quantity of hen egg lysozyme for use in cheese
manufacture can be presented reliable for a secure dosing.
The use of lysozyme in cheese making is legally permitted in the
Federal Republic of Germany for the production of semihard cheese
only. It must not be mixed with nitrate
ENZYME-CHEMICAL ANALYZER ECA 20/ESAT 6660
No full textThe enzyme electrode-based analyzer ECA 20/ESAT 6660 is suited for the
determination of glucose, lactate, lactose, glutamate and lysine. The
function and main features of the analyzer are described and the analytical
parameters outlined
GLUTAMATE OXIDASE BASED BIOSENSORS
No full textThe determination of L-glutamate is important in fermentation control
in foodstuff industry, because many kinds af food contain Glutamate as
an essential flaveur compound, Furthermore, determination of Lglutamine
demanded in on-line control cof mammalian cell culture,
Glutamate produced in enzyme reactions, @.g., by a transaminas
’, can be
& Measure of the respective enzyme activity. These data are of high
value in the diagnosis of heart and liver deseases
AMPEROMETRIC ENZYME ELECTRODES FOR NAD(P)H AND UREA
No full textAmperometric enzyme electrodes for NAD(P)H as well as bienzyme electrodes
for dehydrogenase substrates have been developed on the basis
of the horseradish peroxidase catalyzed aerobic oxidation of reduced
pyridine nucleotides. Limits of detection are: 20 ymol/l NADH or
30 umol/1 NADPH in the HRP electrode and 0.8 umol/1 NAD(P)H, 80 pmol/l
glucose, 100 ywmol/l ethanol and 200 umol/l isocitrate in HRP-dehydrogenase
bienzyme electrodes with cofactor recycling. Relative standard
deviations are 4 %, measuring frequencies 6-8 samples/h.
Other types of amperometric biosensors are based on the electrochenical
hydrazine oxidation. The dependence of the anodic current on the
hydrazine concentration at constant pH values was used to determine
enzyme activities of human serum and bovine eye lens leucine aminopeptidase
(LAP) and of human serum alanine aminopeptidase (AAP). Detection
limits were 5 units/l, the correlation of the results in serum
with the respective optical method was better for AAP then for LAP.
Kinetic constants of bovine lens LAP were found in the same range as
with the optical method.
At constant hydrazine concentration its oxidation current is a linear
function of the hydroxyl ion concentration. This dependence was used
to develop an amperomeric urea electrode.
Typical parameters are: linear range 0.8-35 mmol/l, response time 20s,
relative standard deviation 1%, frequency 40 samples/h and operational
stability two weeks. The urea content in pure solutions, in dialysates
of artificial kidneys and in human serum was determined in good correlation
with Berthelot’s method. Buffer influences were eliminated by
two electrode difference measurements
A MICROBIAL SENSOR FOR BOD
No full textBiochemical oxygen demand (BOD) is a widely used parameter for the
determination of biodegradable organic compounds in waste water. The
conventional BOD test takes 5 days (BODs) and is thus unsuitable for
process control. A more rapid estimation of BOD may be possible by
using a microbial sensor containing whole celis immobilized on an
oxygen electrode. The first report of such a microbial BOD sensor was
published in 1977 by Karube et al. £27. In contrast to microbial
sensors for substrate measurements, which should be highly specific,
the microorganisms for BOD sensors must have a broad substrate
spectrum. Activated sludges obtained from waste water treatment
Plants, which contain a variety of species of microorganisms have been
used in BOD sensors [1,2]. However, it was difficult to prepare
reproducibly working sensors with activated sludge containing mixed
Populations [3]. Sensors using pure cultures of microorganisms seem to
be more suitable, as has been demonstrated with Trichosporon cutaneum
(3-51, Hansenula anomala I[61, Clostridium butyricum [il], Escherichia
coli [71 and Bacillus subtilis [5]. Most BOD sensors employing
an
stationary state measurement exhibit response times of 15 — 20 min
Process control in chemostat experiments
No full textAn integral part of modern bioprocess engineering is on_line measurement and control of
state variables. By this way, many of these variables can be made "culture parameters", i.e
be kept constant. Only this opens the possibilities to provide access to the Civing cell e.g.
- Study kinetics and metabolic control
- control a bioprocess well enough to optimize the objective(s) of the process
- obtain fundamental insights into normal and aberrant cell behaviour.
However, the present state of the art with respect to on_line measurement is far from wha
we need (Schigerl et al., 1987; van Brunt, 1987; Luong et al., 1988).
We are in a satisfactorily comfortable situation considering physical variables because full
advantage of the developments madeinthe field of chemical engineering can be taken.
Considering chemical variables, we suffer most often from the fact that the analytical
methods available are not suited for application within the sterile barrier of monoseptic
bioprocesses. As a result, the measurements are no longer in situ. Moreover, many of those
Sensors are not sufficiently selective for a single substance to be quantified in heterogeneous
culture media. The consequence is the need for a pretreatment of samples and, hence, a
considerable time delay and eventually loss of on_line characteristics and continuous
availability of data.
With respectto biological variables, the worstsituation is faced although these variables are
the keys for optimal bio-process control
STATE OF THE ART AND FUTURE TECHNICAL POSSIBILITIES FOR THE MEASUREMENT OF BIOLOGICAL PARAMETERS (ESP. IN VIVO)
No full textIn recent years progress in the area of semiconductor technology, whichis the result of the
high degree of miniaturization, has led to new technologies and new applications in the
related fields of physical, chemical, and biological sensing mechanisms. Typically for this
trend in medical diagnostics is the shift from the in-vitro analysis to in-vivo determination of
chemical and biological parameters by the replacement of the chemical analytic methods by
chemical sensors. As far as physical parameters in biomedicine are concerned new
applications are being considered.
In order to avoid any contamination and degradation during transportation future systems
under consideration might determine all the parameters ofinterest directly in the organism.
The sensing area will become small enough to receive analytical data from a volume downto
the cell order of magnitude
MINIATURIZED BASIC OXYGEN AND PH SENSORS FOR ELECTROCHEMICAL MEASUREMENTS IN BIOLOGICAL SYSTEMS
No full textAfter an introduction concerning the importance of pH and 0, concentration
in biological systems, two types of sensors were reviewed:
1) amperometric miniaturized electrodes for in vivo oxygen measurements
and as basic sensors for glucose measurements, and
2) ISFET pH-sensors with SizN, membrane.
The miniaturized po. sensors were tested in vivo using narcotized
rabbits and dogs. For the Purpose of use the pH sensors were examined?
range of application, service life, sensitivity, long-time
drift, temperature drift and time of response
STANDORTE UND MÄRKTE FUR BIOPROTEIN - MARKTWIRTSCHAFTLICHE ÜBERLEGUNGEN ZUR PLANUNG VON SCP-ANLAGEN
No full textSummary
To improve the world food situation and to correct a threatening
short supply numerous measures and technologies are being developped,
among them the production of microbial protein.
To attain optimum conditions for production and distribution of
Single-Cell-Protein (SCP), a knowledge of the market, the economical
environment and their future development is necessary.
Raw material costs have substantial impact on the economies of SCPproduction.
Availability and cost of suitable petrochemical or biological
feedstock have to be investigated and balanced against as
well as compared to other possible utilizations e.g. ethanol production.
Animal feed is a relatively non-problematic outlet for SCP. Marketing
strategies are directed by the market potential which depends
on demand and composition of mixed feed, under consideration of
quality-price-conditions. This leads primarily to a price comparison
versus sojmeal and fishmeal. Dominant factor within these considerations
is the feed-industry according to its size and structure.
Especially in countries with a specific protein deficit it seems
reasonable to think of a direct application of SCP in human nutrition.
Essential for the desired effect are, of course, possibilities
of processing and distribution within the food-industry as well
as acceptance of the product by the industry and likewise the consumers.
This concerns prices as well as qualities. Particular habits
in nutrition and the structure of the food supply system should, by
any means, be carefully investigated already in the planning stage
AMPEROMETRIC AMINO ACID ELECTRODES
No full textDetermination of amino acids is highly demanded in food analysis, fermentation
control and the chemical laboratory. Enzyme membrane electrodes
have been successfully applied for the measurement of glutamate
/1/, lysine /2/ and tyrosine /3/ in foodstuffs. The determination
of amino acids using a chemically modified enzyme electrode has
been described TAGS/
The aim of the present investigations is the comparison of the analytical
performance of monoenzyme electrodes for L-glutamate, L-lysine
and L-tyrosine using selective oxidases with that of a sensor based
on group-specific L-amino acid oxidase (L-AAOD). Furthermore, lysine
Oxidase, glutamate oxidase and tyrosinase have been coimmobilized in
front of an Oxygen electrode to give a sensor which responds to the
respective amino acids in mixtures