Ch. 3— Genetic Engineering and the Fermentation Technologies • 51 
• rai'holndrates, such as fructose sweeten- 
ei's: 
• lipids, such as \ itamins A, E, and K; 
• alcohols, such as ethanol; 
• other oi'ganic compounds, such as acetone: 
and 
• inorganic chemicals, such as ammonia, for 
use in fertilizers. 
Fermentation is not the onh' \\a\ to manufac- 
ture or isolate these products. Some are tradi- 
tionalK produced hy other methods. If a change 
from one pi'oeess to anothei' is to occur, both 
economic and societal pressures \\ ill help deter- 
mine whether an inno\ati\e a[)proach will he 
used to [)i'oduce a [)ai ticular product. .Alan Bull 
has identified four stimuli for change and in- 
no\ ation:' 
1. abundance of a [jotentially useful raw 
material: 
2. scarcitx’ of an established product; 
3. disco\ ery of a new product: and 
4. en\ ironmental concei'iis. 
.And conditions e.xisting toda\ ha\ e added a fifth 
stimulus: 
5. scarcity of a currently used raw material. 
Each of these factors has tended to accelerate 
the application of fermentation. 
1. Abundance of a potentially useful raw ma- 
terial.— The use of a raw material can be 
the dri\ ing force in dex eloping a process. 
When straight chain hydrocarbons (n-al- 
kanes) were produced on a large scale as 
petroleum refinery byproducts, fermenta- 
tion processes were developed to conxert 
them to single-cell proteins for use in ani- 
mal feed. 
2. Scarcity of an established product.— The 
new-found potential for producing human 
hormones through fermentation technol- 
og\' is a major impetus to the industry to- 
day. Similarly, many organic compounds 
once obtained by other processes— like 
citric acid, which was extracted directly 
'.A. T. Bull, D. C. Elluood, and C. Ralledge, Microbial Technology: 
Current State, Future Prospects, 29th Symposium of the Society tor 
(ieneral .Microbiologx' at University of Cambridge. .April 1979 
(Cambridge. England: Cambridge University Press. 1979). pp. 4-8. 
from citrus fruits— are now made hy fer- 
mentation. .As a result of more efficient 
technology, pi’oducts from \itamin B,, to 
steroids ha\ e come into w ider use. 
3. Discovery of a new product.— The discox erv 
that antibiotics were produced hy micro- 
organisms sparked searches for an entirely 
new group of jii'otlucts. Several thousand 
antibiotics have been discovered to date, of 
w hich over a hundred have proved to be 
clinically useful. 
4. Environmental concerns.— I'he problems of 
sewage treatment and tbe need for new 
sources of energy have triggered a search 
foi' methods to convert sewage and munici- 
pal wastes to methane, the principal com- 
ponent of natural gas. Because micro-orga- 
nisms play a major role in the natural cy- 
cling of organic compounds, fermentation 
has been one method usetl for the conver- 
sion. 
5. Scarcity of a currently used raw materi- 
al.— Because the Earth’s supplies of fossil 
fuels are rapidly dwindling, there is intense 
interest in finding methods for converting 
other raw materials to fuel. Fermentation 
offers a major approach to such conver- 
sions. 
Fermentation technologies can be effective in 
each of these situations because of their out- 
standing versatility and relative simplicity. The 
processes of fermentation are basically identi- 
cal, no matter what organism is selected, what 
medium used, or what product formed. The 
same apparatus, with minor modifications, can 
be used to produce a drug, an agricultural prod- 
uct, a chemical, or an animal feed supplement. 
Fermentation using whole living cells 
Originally, fermentation used some of the 
most primitive forms of plant life as cell fac- 
tories. Bacteria were used to make yogurt and 
antibiotics, yeasts to ferment wine, and the 
filamentous fungi or molds to produce organic 
acids. More recently, fermentation technology 
has begun to use cells derived from higher 
plants and animals under growdh conditions 
known as cell or tissue culture. In all cases, 
large quantities of cells with uniform character- 
