Ch.6 — The Food Processing Industry • 109 
Genetic engineering and 
SCP production 
Despite the miei'ohial screening studies that 
ha\e been conducted and the wealth of basic 
genetic knowledge a\ailahle about common 
\east (a majoi' source of SCP), genetic engineei'- 
ing has had little economic impact on S(d’ proc- 
esses until recently. Today, a \ariety of sub- 
stances are being considered as raw materials 
for con\ersion. 
• Petruleum-bnsrd hydrocurbons.—ViuW re- 
centh’, the w ide a\ ailahility and low cost of 
peti'ochemicals ha\ e made the /j-alkane hy- 
drocarbons (straight chain molecules of 
carbon and hydrogen), which are petro- 
chemical by{)roducts, potential raw materi- 
als for SCd’ production. .At British Petro- 
leum, mutants of micro-organisms ha\e 
been obtained ha\ ing an increased protein 
content. .Mutants ha\e also been found 
with other increased nutritive \ alues, e.g., 
vitamin content. 
• Methane or met/tano/.— Relatively few ge- 
netic studies have been directed at in\ esti- 
gating the genetic control of the microbial 
use of methane or methanol. However, one 
recent application of genetic engineering 
has been reported bv the Imperial Chem- 
ical Industries (ICI) in the United Kingdom, 
where the genetic makeup of a bacterium 
{Methylophilus methylotrophus) has been 
altered so that the organism can grow 
more readily on methanol. The increase in 
growth pro\ ides increased protein and has 
made its production less expensive. The 
genetic alteration was accomplished by 
transferring a gene from Escherichia coli to 
M. methylotrophus. 
• Carbohydrates.— Many carbohydrate sub- 
strates— from starch and cellulose to beets 
and papermill wastes— have been investi- 
gated. Forests are the most abundant 
source of carbohydrate in the form of cel- 
lulose. But before it can be used by micro- 
organisms, it must be transformed into the 
carbohydrate, glucose, by chemical or en- 
zymatic pretreatment. Many of the SCP 
processes that use cellulose employ orga- 
nisms that produce the enzyme cellulase, 
w hich degrades cellulose to glucose. 
Most of the significant genetic studies on the 
pi'oduction of cellulase by micro-organisms are 
just beginning to appear in the literature. I'he 
most recent experiments have been successful 
in ci'eating fungal mutants that produce excess 
amounts. 
Commercial protluction 
Of the estimated 2 million tons of SCd’ pro- 
duced annually thi'oughout the w'orld, most 
comes from cane and beet molasses, w'ith about 
oOO, ()()() tons from hydi'olyzed wood wastes, 
corn trash, and papermill wastes. (See table 23.) 
Integrated systems can he designed to couple 
the production of a product oi- food with SCP 
production from wastes. E.g., the waste saw- 
dust from the lumber industry could become a 
source of cellulose for micro-organisms. Id’s 
successful genetic engineering of a micro-orga- 
nism to increase the usefulness of one raw 
material (methanol) should encourage similar 
attempts for other raw materials. 
But while SCP can he obtained from a wide 
variety of micro-organisms and raw' materials, 
the nutritional value and the safety of each 
micro-organism vary widely, as do the costs of 
competing protein sources in regional markets. 
Consequently, accurate predictions cannot be 
made about the likelihood that SCP will displace 
traditional protein products, overall. Displace- 
ments have and will continue to occur on a case- 
by-case basis. 
Table 23.— Raw Materials Already Tested on a 
Laboratory or Small Plant Scale 
Agave juices 
Pulpmill wastes 
Barley straw 
Sawdust 
Cassava 
Sunflower seed husks 
Citrus wastes 
(treated) 
Date carbohydrates 
Wastes from chemical 
IVleatpacking wastes 
production of maleic 
IVIesquite wood 
anhydride 
Peat (treated) 
Waste polyethylene (treated) 
SOURCE: Office of Technology Assessment. 
