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AROMASTOFFE ALS SYNTHESEZIELE NEUER BIOTECHNOLOGIEN
No full textMicroorganisms or microbial enzymes synthesize flavour and aroma compounds
in traditional processes for the production of fermented food.
Initiated by the consumer preference for natural flavours and an
increasing industrial demand, biotechnological sources of flavour
have begun to attract industrial and academic research. The use of
enzymes was suggested to produce monoterpene alcohols, fatty acids,
methylketones, aliphatic and terpenoid esters, cinnamic acid derivatives
or complex food flavours, such as cheese flavour. Cofactor-coupled
reactions yielded methylbutanal, geranial or cinnamic aldehyde from
their corresponding alcohols. The formation of "green" notes or of
vegetable flavours was achieved using naturally or artificially immobilized
plant enzymes: In the field of DProcasyotic.,cells, a “clear
trend towards continuous bioprocesses and (re)combined Genetic inkormation
is noted. Higher fungi, in particular Basidiomycetes with
their impressive metabolic diversity, open a direct access to many
flavour moleculs which were formerly thought to be restricted to
higher plants. Bioconversions and de novo syntheses on defined and
complex media yielded single compounds, such as "fruit' esters, terpenols,
alkanolides or phenylpropanoid compounds, and also mixtures
of volatiles. As for other bioprocesses, critical steps are strain
selection, improvement of cultivation conditions and yields, and
product recovery from the bioreacto
NUTZUNG VON ENZYMKOMPLEXEN AUFGESCHLOSSENER ZELLEN FUR DIE FERMENTATIVE BEHANDLUNG VON LEBENSMITTELMASSEN
No full textThe biotechnology for flavour-production is using biocatalysts in form of single
enzymes or of composed enzymes for the production of natural flavours. This is
causing a lot of advantages, e.g. the selective formation of flavours or the
formation of complex flavour systems by aid of composed enzymes from ruptured single
cells. In addition it is possible to use specific precursors in order to enrich
specific flavours in a selective way. Because composed enzymes can be used in higher
concentrations and without borders for the mass-transfer, ripening processes can be
accelerated.
One has to differentiate between direct ripening and non-direct ripening of foods.
Direct ripening allows a process "in situ", non-direct ripening can be used for
production of specific aroma-concentrates.
Because food quality depends on flavour composition, we get by this way a big chance
to improve either the quality of our food products or the economics of the process,
e.g. by reducing the ripening time. We should keep in mind that besides flavour also
other quality affecting parameters, e.g. texture can be improved by using composed
enzymes. Therefore biotechnology offers a lot of new ways for the natural improvement
of food products
PULPA-VORBEHANDLUNG ZUR VERMINDERUNG DER AZIDATION DER SAMEN WAHREND DER KAKAOFERMENTATION IN MALAYSIA
No full textIn a cooperational programme between the Botanisches Institut,
Technische Universität Braunschweig and the Malaysian Agricultural
Research and Development Institute two new fermentation methods were
developed, which are able to solve the problems of high acidity and
weakness in cocoa flavour of Malaysian cocoa. By post harvest pod
storage or limited pulp surface drying before fermentation the volume
of the cocoa pulp surrounding the beans is reduced. The thereby
caused better aeration of the pulp in the early phase of fermentation
favours the direct respiration of sugars to carbondioxide and water
by yeasts and suppresses the anaerobic ethanol fermentation and acetic
acid production by yeasts and acetic acid bacteria. The higher
seed pH during the time of enzymatic flavour precursor formation
results in a better flavour potential of the cocoa beans
BIOSENSOREN IN DER LEBENSMITTELINDUSTRIE
No full textBiosensors are sensors containing immobilized biological material as the sensitive
part (enzyms, antibodies, microorganisms, organelles, whole cells). Besides the
biological material biosensors contain an integrated optical or electrical transducer. The advantage of biosensors compared to purely physical sensors is their
high selectivity. It is possible to determine single components in a complex mixture without time consuming sample-preparations.
The micro-electronical part provides a high sensitivity. So it is possible to measure very low concentrations in mixtures of chemically similiar compounds. The development of biosensors has grown very fast during the last years. Actually medical
applications are dominant, because only the pharmaceutical industry producing highvalue added products is able to finance the high R & D costs in the course of their
biotehchnological research. In the near future these results will be used in other
applicaton fields, like the environmental technology or the food industry. For the
food industry some commercially available biosensors are existing, for example a
biosensor to determine the freshness of fishes or another one to determine the
freshness of fats and oils. These two developments come both from Japan
MÖGLICHKEITEN DER GENTECHNOLOGIE FUR DEN NAHRUNGSMITTELBEREICH
No full textDie meisten bei der Lebensmittel- und Genußmittelherstellung verwendeten Enzyme
stammen aus Mikroorganismen. Handelt es sich bei der zu katalysierenden Umsetzung um eine Ein- oder Wenigschrittreaktion, wird das Enzym bzw. Enzymgemisch dem umzusetzenden Rohprodukt zugemischt. Alternativ zu dieser EinwegStrategie bietet sich eine Enzym- Trägerfixierung an. Sind bei der angestrebten
Umsetzung mehrere enzymkatalysierte Schritte nötig, so sind diese Vielschrittumsetzungen in der Zelle als Reaktionsraum am besten durchführbar, da ja die
Zelle nichts anderes als eine Trägermatrix darstellt, an der eine Vielzahl von
Enzymen fixiert sind. Abhängig vom Endprodukt kann es vorteilhaft sein, auch
Zellen an Träger zu fixieren, nicht nur, um einen Prozeß kontinuierlich zu gestalten,
sondern auch um die Zellen einfacher aus dem Produkt abtrennen zu können
KNOWLEDGE-BASED PROTEIN MODELLING AND DESIGN
No full textKnowledge-based modelling can be envisaged as a number of steps concerned with the
establishment and use of rules to generate a model of a protein. One of the most powerful
procedures in learning rules is comparison of related Structures either through
alignment of sequences to identify conserved residues or superposition of three dimensionalstructures
to identify conserved conformations or motifs. Thus the first step in a
knowledge-based modelling procedure is the systematic comparison of families of topologically
similar structures. This step will lead to the establishment of "equivalences"
between the structures compared and to their clustering based on measures of similarity.
The second step involves the projection of the results of the comparisons of three
dimensional structures down onto the level of sequence. This step establishes rules
relating sequence to structure. These can be expressed as consensus sequences - templates
- for topologically equivalenced residues, or as key residues in canonical structures,
which are then used to align the sequence of the protein of unknown tertiary
Structure. The third step uses the rules established in the second step to generate a
three-dimensional model
THE CLASSIFICATION OF THE CYTOPHAGA-LIKE BACTERIA
No full textBased on a thorough study of a considerable number of strains, most of them newly
isolated, we believe that the taxonomy of the cytophagas and related organisms has to
be reconstructed from its very base. Using GC and DNA-DNA hybridization data as well
as chemosystematic, physiological, biochemical and morphological observations, the
following groups can be recognized with some confidence: Sporocytophaga, Flexibacter
(in the original sense), Lysobacter, and Sphaerocytophaga/Capnocytophaga. The remaining
bulk of strains, classified now as Cytophaga/Flexibacter (the latter in a sense
deviating from the original definition) comprises with certainty several different
genera, and the genus Cytophaga s. str. may finally have to be restricted again to
aerobic cellulose-decomposing soil organisms. With the exception of a few rare cases,
our present knowledge does not allow us to reliably distinguish between species
CELL DEATH DURING FRUITING BODY FORMATION IN MYXococcus
No full textMassive cell death occurs during fruiting construction by several species
of Myxococcus . The events which occur lead us to the hypothesis that
regulated senescence and cell death are integral part of myxobacterial
development. During fruiting body formation by M. xanthus 60 - 8) % of
the vegetative cells lyse. The majority of the survivina cells are eventually
converted to myxospores in the fruiting body. This lysis has been
measured both by the loss of 3y-methy1 thymidine label from DHA of the
cells and by actual cell counts. Such lysis occurs under a variety of
conditions leading to fruiting body formation. We have also demonstrated
lysis during fruiting body formation in Myxococcus fulvus and Myxococcus
virescens.
If cells are removed at various times during fruiting body formation and
replaced in a liquid growth medium the tendency to lyse is reversible
until the fruiting bodies have formed; at that time the vegetative cells
become irreversibly committed to lysis.
We suggest that lysis in the organisms we have examined is a functional
and necessary part of the developmental cycle. It is possible that the
lysing cells are providing a source of biosynthetic precursors and/or
a source of energy for the formation of myxospores and/or fruitina
bodies
RECORD OF THE TECHNICAL DISCUSSION AT THE SYMPOSIUM
No full textThe majority of the people present voted for having also in future a
symposium on myxobacteria every year. To allow sufficient time for
planning and raising funds, however, the place of the meeting should
be decided upon 2 years in advance. The meeting should alternate regularly
between both sidesof the Atlantic.
An invitation has been extended by our colleagues in California to
arrange the next meeting at the Asilomar Conference Grounds, Pacific
Grove, California. The invitation was gratefully accepted, and July
25 to 27 was suggested as the most desirable time for the meeting.
(This date has been verified in the meantime. H.R.)
Ian Sutherland proposed that he would contact Colin Clarke and Howard
Parish for chances to arrange the 1977 meeting in the United Kingdom.
This was approved.
The majority decided to restrict also future symposia on the biology
of myxobacteria and to exclude other gliding bacteria. However, people
from other fields of research may be invited to participate in the
meeting.
There was agreement not to publish a detailed symposium's report. Only
the summaries of the lectures should be distributed.
In order to be able to trace back quickly experimental strains to their
origin, it was agreed upon to suggest for general adaption the labelling
system which was proposed at the Cold Spring Harbor meeting: Each
strain should be identified by the initials of the individual who isolated
the strain or, if this is not feasable, who first introduced it
into the literature. Furthermore, different strains of one species
coming from one person should be numbered consecutively, the numbering
beginning anew with another species; e.g. Myxococcus xanthus RBl,
strains is independent of designations given the strain in individual
laboratories, and should always remain attached to the name of the
strain whenever anything is published about the strain and regardless
who works with it later on. When a strain is sent to another individual,
care should be taken to supply the original labelling with the strain.
The complete history of the strain should be given when the strain is
introduced into the literature for the first time. (Note added when
writing down the Record: to avoid repeated labelling of one strain
care should be taken to adopt as label the initials of the person who
originally isolated and distributed the organism, for he might have
sent the same strain to different laboratories. If necessary the label
should be inquired from the original source of the strain. H.R.)
Robert P. Burchard has been asked at the Cold Spring Harbor meeting
to work out a system for the designation of mutants. His proposals
have already been made public in the Myxobacterial Messenger. They
were unanimously approved, suggested for general use, and may be cited
here again:
The system is based on that proposed by Demerec et al. (Genetics 54:
61 - 76, 1966).
"Briefly, genus and species names should be followed by the initials
of the describing investigator (first and last names). He or she would
then assign a number to the strain, starting with 1. Each investigator
should keep a log book with a list of his strains, their origin
and history, and their genotype and/or phenotype. The latter could be
accomplished with Demerec et al "3 letter plus" abbreviations. Using
my strains as an example:
M. xanthus RB1 derived from Dworkin's FB as a stable tan and called
strain FB, to date. The phenotype nomenclature would be Tan-1.
RB4 is my non-motile NM, derived from SM which in turn is derived
from FB.
The phenotype designation Cam-r25 means resistant to 25 ug chloramphenicol/
ml.
For genotype, lower case lettering is used. Thus, a methionine-requiring
auxotroph might be designated as "met-1". The hyphen could
be replaced by a letter (capital ) when mapping is accomplished".
It was again urged to make better use of the Myxobacterial Messenger
(M.M.) to our mutual benefit. Completed Ph.D. theses on gliding bacteria
should be reported to the M.M. and a brief abstract supplied.
Planned gatherings of myxobacteria people at ASM meetings should be
announced early in the M.M..
As already suggested at the Cold Spring Harbor meeting each laboratory
should sent a list of available strains, including mutants, to
the M.M..
At the Cold Spring Harbor meeting it has been suggested to start
a central collection of all myxobacterial strains including mutants
available. Martin Dworkin inquired in the meantime from Ellis Brockman
if he would be willing and in a position to keep such a collection.
This is not the case. Hans Reichenbach promised to ask at the Deutsche
Sammlung von Mikroorganismen (German Collection of Microorganisms) in
Göttingen whether they would be willing to accept such a collection.
(Note added when writing down the Record: The policy of the Deutsche
Sammlung von Mikroorganismen does not allow to keep such a specialized
collection. H.R.)
ENZYME SENSORS FOR BIOTECHNOLOGICAL PROCESSES AND PRODUCTS
No full textEnzyme sensors have been developed usina coupled enzyme
reactions to determine the concentrations of the biotechnoloay
products starch, pullulan, oligosaccharides. maltose. the
low-calorie sweetener maltitol. glutamine, and enzyme activities
of alpha-amylase and pullulanase. These enzyme sensors have been
tested to control enzyme production by immobilized cells and
also animal tissue cultures