biotechnology — its past, present and future
TRANSCRIPT
Biotechnology Letters Vol. 2 No.4, lol-106 (1980)
Bi OTECHNOLOGY - ITS PAST, PRESENT AND FUTURE
Dr. J. de Flines, Gist-Brocades, Delft, The Netherlands.
Microorganisms multiply faster than cells of higher plants or animals.
They can live in a relatively simple nutritional environment and they
are able to produce an astonistring variety of products. Some - not all -
are unicellular and easy to handle. Their adaptive capacities are very
impressive.
As the causative agents of the plague and other pestilences, micro-
organ i sms - especially bacteria - have a very bad reputation. Since
time immemorial, however, man has used microorganisms - though unknow-
ingly until fairly recently - for the production of useful goods often
with very pleasant properties and effects (except when used excessively).
Wine, beer, cheese and other foods are well-known m
as is - in a sense - our daily bread.
Since the middle of the 19th century, biology and m
developed into the sciences as we know them today. T
crobial products,
crobiology have
hey were followed
later by biochemistry, biophysics and biotechnology, disciplines that
connect biology to other sciences: chemistry, physics and technology.
This brings us to the recent past - hardly hidden and perhaps already
sh i n i ng - and to the present. Where are we now; where are we going?
Currently, microorganisms are applied in four different ways:
IR They are produced for the use of whole cells. Probably the most
important example is bakers’ yeast. But mushrooms are increasingly
becoming part of our diet, and single cell protein, produced for
feed and possibly food purposes, also belongs to this category.
R For the production OF metabolites. To this class belong ethanol, al I
antibiotics that are produced by fermentation, and such organic
compounds as citric acid and glutamic acid.
f As biocatalysts in specific reactions. This may be done in two
different ways: the organisms as such may be the catalytic system
or a specific enzyme may be isolated from it and applied.
fi For the purification of waste water in an aerobic or anaerobic
process.
TO this point I have only discussed the microbiological component of
biOt8ChnOlOgy, but the role of technology itself should not be over-
looked. Not on 1 y have a I I recovery processes and tltt? cons t rut i ion
of fermenters needed the expertise of chemists and process erqineers,
but a I so the fermentat ion per se requires that i npul .
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And it is perhaps worthwhile to look at some of the peculiarities of
using microorganisms on a large scale. The largest conventional fer-
menters of the moment are about 450 m3. Therein, the organism is cul-
tured in a liquid medium, in a so-called submerged fermentation.
In aerobic fermentation, air supply and usually stirring are neces-
sary-to provide the microorganism with the required oxygen. Stirring
is particularly important when fungi or actinomycetes are the produc-
tion organisms, because these are filamentous.
Contamination by other microorganisms must be avoided, hence supplied
air and the culture medium must be sterile and aseptic conditions
must be maintained throughout the fermentation. Sometimes it is possible
to favour growth of the production strain by choosing extreme condi-
tions, such as methanol as the carbon source in SCP-production, or
low pii in growing yeast. But even then sterile conditions are an abso-
lute necessity. Continuous feeding of nutrients during the fermentation
- a normal occurrence in batch operations - requires the feed to be
sterile, and the same holds for the antifoam and the additions of acid
or base for pH-control.
All this might appear rather easy. But those experienced in the field
will agree that it is no light task to run a farge fermentation plant
or process, utilizing a slow grower on an opulent medium at neutral pH
for about a week’s time and repeat this the year round without at least
a few percent loss through infections.
Fermenters may be universally applicable in biotechnology, the isola-
tion of the fermentation product is another matter. Here diversity
really starts. Let us have a closer look at a practical example: the
production of benzylpenicillin. The fermentation s a fed batch process
in which sugar solution is continuously fed into t he fermenter.
Phenylacetic acid, as a solution of its potassium salt, is also added
as a precursor for the side chain of benzyl penic Ilin.
At the completion of the fermentation, the thick broth is filtered
through a continuous, rotating filter, the mycelium is washed, and
filtrate plus washing are extracted with butylacetate in a counter-
current extractor. fhe extract is supplied with a source of potassium
ions in order to obtain the crystalline potassium salt of benzyl peni-
cillin. This is filtered off on a rotating filter, slurried in butanol,
filtered and dried, yielding a constant stream of the potassium salt
of penicillin at 99.5% purity.
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Let us, for a moment, consider the economics of this process. Raw
materials and energy constitute about 60% of the total costs, and the
so-called fixed costs account for the other 40%.
this is the usual picture for fermentations of-this type. The
costs do not include expsnditures for waste water treatment. When
this is required, aerobic or anaerobic treatment is available, as the
waste is readily biodegradable. However, the treatment adds consid-
erably to the cost, because the spent fermentation liquor has a high
BOO content. A plant of reasonable capacity may be equivalent in BOO
to a city of say 300,000 inhabitants. The penicillin thus obtained
sel Is for about $ 35 a ki iogramme.
Relatively short fermentations in large volumes with high product
yields will result in low cost prices. This is the situation with
citric and glutamic acid. In contrast, for the production of a rare
chemical, such as hydrocortisone which sells for about $ 800 per
kilogramme, fermentation, although expensive, will be competitive
when chemists are not clever enough to introduce readily an oxygen
atom at the so-called 113-position. This also applies. to degradation
of the side chain of sitosterol, a process carried out on a large scale
by three companies in the world, yielding the steroid intermediate
androstenedione.
It is no exaggeration to state that biotechnology up to the present
has made tremendous contributions to industry. A diversity of pro-
cesses is used in the manufacture of many different products, such as:
alcoholic beverages, baker’s yeast, single cell protein, eth.anoI
L-amino acids, citric acid, xanthan gums, antibrotics, steroid hormones,
enzymes and vaccines. Microbiology is at the bottom of aerobic and
anaerobic waste water treatment and microbial mining.
A review of the present status of biotechnology would be highly
inadequate without mention of the fantastic recent achievements in
molecular biology. -By “genetic engineering” cells may be constructed
that make enzymes and other proteins which they do not normally pro-
duce, and hence possibly other metabolites as well.
Let us now try to look from the already shining present of biotechnology
into the future in which i-ts brilliance may still increase.
A The price of oil has risen dramatically in the seventies. Rather late
the industrial countries have realized that alternative energy sctur-
ces must be developed.
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Plants, using solar energy by photosynthesis, may be used as a direct
energy source - which is renewable - by burning them, or by using
them indirectly via bioconversion into easily transportable methanol
or ethanol. Of all photosynthesized carbohydrates, three are of mayor
importance: cellulose, starch and saccharose. The latter two are
easily converted, but conversion of wood with its lignin and cellu-
lose constituents by enzymes or whole microorganisms is still an
unsolved problem, at least if processing is to be economically jus-
tified. Very likely, methods will be discovered that solve the prob-
lem. But it is obvious that in the near future only certain regions
in the world - Brasi I, the Mid-West of the USA and Canada - will be
suitable for the economic, large scale production of an energy car-
rier, such as ethanol, from agricultural sources. For Western Europe
the opportunities are probably less.
fi Biomass produced through photosynthesis could be used as the starting
material In biotechnical production processes for bulk chemicals.
A Production of more complex molecules-by fermentation. Without any
doubt genetic engineering will greatly extend the possibilities in
the next decade. Human insulin is about to be produced by fermenta-
tion, interferon will probably follow soon. A vast new field seems
to be opening up with opportunities for fine chemicals and pharma-
ceuticals.
A Enzymes will be used increasingly, and immobilized enzymes with their
improved stability, often at higher temperatures, should gain in
Importance.
A Waste water treatment today is often carried out by aerobic fermen-
tation, a process that consumes much energy, creates a large quanti-
ty of sludge, is expensive and requires heavy investments.
Anaerobic treatment and more sophisticated aerobic processes will
certainly be developed.
A A short remark about using cells of higher organisms. Vaccine pro-
duction by using special cell lines is well known. Plant cells can
be cultured and are able to produce desired substances. Their slow
growth and rather low production rates argue against use on an in-
dustrial scale. But progress will be made in this area, possibly
also through genetic engineering.
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From this review you may conclude that my expectations about the future
role of biotechnoitigy are optimistic. But allow me to sound one warning.
Recent reports in the press and the other media, and also those from
learned institutions, have become almost jubilant about the possibiii-
ties of applied biotechnology. This might make the false impression that
realizing these opportunities wJii be an easy task. In my opinion the
contrary is true. A great deal of fundamental and applied research work
will be needed and only a concentrated effort will enable us to reap
ail th-e benefits of biotechnology.
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