biotechnology — its past, present and future

5
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 1y 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 . 159

Upload: j-flines

Post on 06-Jul-2016

228 views

Category:

Documents


2 download

TRANSCRIPT

Page 1: Biotechnology — Its past, present and future

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 .

159

Page 2: Biotechnology — Its past, present and future

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.

160

Page 3: Biotechnology — Its past, present and future

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.

161

Page 4: Biotechnology — Its past, present and future

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.

162

Page 5: Biotechnology — Its past, present and future

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.

163