Ch. 3— Genetic Engineering and the Fermentation Technologies • 53 
incli\ iilual steps to c'omj)lete the com ersion. In a 
cliemical synthesis, the I'aw mattM’ial (shown in 
t'if^ure 19 as a) might have to he transtbnned to 
an intermediate h. w liich, in tiii’ii, might lia\ e to 
he comerted to intermediates c and d het'ore 
final comei'sion to the [)rodiict e— eacli step 
necessitating the recovery of its products before 
tlie next con\ersion. In fei'mentation technol- 
og\', all steps take place within those miniature 
chemical factories, the micro-oi'ganisms; the 
microbial chemist merely adds the I'aw material 
a and reco\ ers the pioduct e. 
A v\ ide \ ariety of cai'holndrate raw materials 
can be used in fermentation. These can he pure 
substances (sucrose or table sugar, glucose, or 
fructose) or complex mixtures still in their 
original form (cornstalks, potato mash, sugar- 
cane, sugar beets, orcellulose). They can he of 
recent biological origin (biomass) oi' derived 
from fossil fuels (methane or oil). The availabili- 
ty of raw' materials varies from country to coun- 
Figure 19.— Diagram of Conversion of 
Raw Material to Product 
a) Chemical conversion 
a 
-►b 
V 

-►d 
J 
►e 
Raw 
material 
Intermediate 
products 
Final 
product 
b) Biological conversion 
material product 
3) In the chemical conversion of raw material a to final 
product e, intermediates b, c, and d must be synthe- 
sized. Each intermediate must be recovered and purified 
before it can be used in the next step of the conversion. 
b) A cell can perform the same conversion of a to e, but 
with the advantage that the chemist does not have to 
deal with the intermediates: the raw material a is simply 
added and the final product e, recovered. 
SOURCE: Office of Technology Assessment. 
try and even from region to region within a 
country; the economics r>f the production proc- 
ess varies accordingly. 
The cost of the raw material can contribute 
significantly to the cost of [troduction. Usually, 
the most useful micro-organisms are those that 
consume reatlily available inexpensive raw' ma- 
terials. For large volume, low-priced products 
(such as commodity chemicals), the relationshi|) 
between the cost of the i'aw material and the 
cost of the end product is significant. For low 
volume, high-priced products (such as certain 
pharmaceuticals), the relationship is negligible. 
The process of enzyme technology 
.Although live yeast had been used for several 
thousand years in the production of fermented 
foods and beverages, it was not until 1878 that 
the active agents of the fermentation process 
were given the name "enzymes” (from the 
Greek, meaning "in yeast”). The inanimate 
nature of enzymes was demonstrated less than 
two decades later when it was shown that ex- 
tracts from yeast cells could effect the conver- 
sion of glucose to ethanol. Finally, their actual 
chemical nature was established in 1926 with 
the purification and crystallization of the 
enzvme urease. 
Fermentation carried out by live cells pro- 
vided the conceptual basis for designing fer- 
mentation processes based on isolated enzymes. 
A single enzyme situated within a living cell is 
needed to convert a raw material into a prod- 
uct. A lactose-fermenting organism, e.g., can be 
used to convert the sugar lactose, which is 
found in milk, to glucose (and galactose). But if 
the actual enzyme responsible for the conver- 
sion is identified, it can be extracted from the 
cell and used in place of a living cell. The 
purified enzyme carries out the same conver- 
sion as the cell, breaking down the raw material 
in the absence of any viable micro-organism. An 
enzyme that acts inside a cell to convert a raw 
material to a product can also do this outside of 
the cell. 
Both batch and continuous methods are used 
in enzyme technology. However, in the batch 
method, the enzymes cannot be recovered eco- 
i'if 
