Ch. 7— The Use of Genetically Engineered Micro-Organisms in the Environment • 121 
obtained bv microbial t'ermentation could com- 
pete with those obtained from alternative 
sources, especially seau eed. C'ontrolled fermen- 
tation is not affected by mai'ine pollution and 
weather, and pi'oduction could be geared to 
market demand. 
Biological processes have disadvantages pri- 
marily in the costs of appro[)riate raw materials 
and in the need foi- large (juantities of solvent. 
(Current efforts to find cbeapei’ raw materials, 
such as sugar beet pulp and starch, show prom- 
ise. The need for solv ents to precipitate and con- 
centrate the polymers before shipment from 
plant to field can be circumvented by producing 
them onsite. 
I Micro-organisms can also produce substances 
j like butyl and propyl alcohols that can be used 
I as cosurfactants in PX)K. It has been calculated 
that if n-butanol were used to produce crude oil 
at a level of 5 percent of l^S. consumption, 2 
billion to 4 billion lb per year— or four to eight 
times the current butanol production— would 
be required. Micro-organisms capable of pro- 
ducing such surfactants have been identified, 
and genetically superior strains were isolated 
several decades ago at the Northern Regional 
Research Udioratories in Illinois. Other chem- 
icals, such as alcohols that increase the rate of 
formation and stability of chemical/crude oil 
mi.xtures and the agents that help prevent pre- 
cipitation of the surfactants, have also been pro- 
duced by microbial systems. 
The uncertainties of the technical and eco- 
nomic parameters are compounded by the lack 
of sufficient field experiments. Laboratory tests 
cannot be equated with conditions in actual oil 
wells. Each oil field has its own set of character- 
istics— salinity, pH (acidity and alkalinity), 
temperature, porosity of the rock, and of the 
crude oil itself— and an injected chemical be- 
haves differently in each setting. In most cases, 
not enough is known about a well’s characteris- 
tics to predict the nature of the chemical/crude 
oil interaction and to forecast the efficiency of 
oil recovery. 
use water available at site: grou-th under conditions that discour- 
age the growth of unwanted micro-organisms: no major problems 
in culturing the bacterium: and genetic stability. 
I.\ SlTl' USE OF MICRO-ORGANISMS 
One alternative to growing micro-organisms 
in large fermenters then extracting their chem- 
ical products and injecting them into wells, is to 
inject the micro-organisms directly into the 
wells. They could then produce their chemicals 
in situ. 
I’nfortunately, the geophysical and geochem- 
ical conditions in a reservoir seldom favor the 
growth of micro-organisms. High temperature, 
the presence of sulfur and salt, low oxygen and 
water, extremes of pH, and significant engi- 
neering hurdles make it difficult to ov'ercome 
these limitations. The micro-organisms must be 
fed and the microenvironment must be care- 
fully adjusted to their needs at distances of hun- 
dreds to thousands of feet. The oil industry has 
already had discouraging experiences with 
micro-organisms in the past. In the late 1940’s, 
for instance, the injection of sulfite-reducing 
micro-organisms, along with an inadvertently 
high-iron molasses as a carbon source, resulted 
in the formation of iron sulfide, which clogged 
the rock pores. One oil company developed a 
yeast to break down petroleum, but the size of 
the yeast cells (5 to 10 micrometers, /im) was 
enough to clog the l-/xm pores. 
Nevertheless, information from geomicrobi- 
ologv' suggests that this approach is w'orth pur- 
suing. Preliminary field tests have also been en- 
couraging. The injection of 1 to 10 gal of Bacillus 
or Clostridium species, along with a water- 
suspended mixture of fermentable raw materi- 
als such as cattle feed molasses and mineral 
nutrients, has resulted in copious amounts of 
carbon dioxide, methane, and some nitrogen in 
reservoirs. The carbon dioxide made the crude 
less viscous, and the other gases helped to 
repressurize the reservoir. In addition, large 
amounts of organic acids formed additional car- 
bon dioxide through reactions with carbonate 
minerals. The production of microbial sur- 
factants further aided the process. 
Although previous assessments have argued 
that reservoir pressure is a significant hin- 
drance to the growth of micro-organisms, more 
recent studies indicate the contrary. The micro- 
organisms must, however, be selected for in- 
creased salt and pH tolerance. 
