96 • Impacts of Applied Genetics— Micro-Organisms, Plants, and Animals 
or lli(’ 1.’), ()()() known species of insects, only 
200 are harniliil enongl'i to warrant control or 
(l('strnction. fortunately for man, most of them 
are sensitive to cei’tain micro-organisms which, 
il they are not toxic to man, nontarget animals, 
and |)lants, can he used as commercial insec- 
ticides. 
,\p|)ro\imately 100 known species of bacteria 
are pathogenic (disease causing) to insects, hut 
only [hvee— Bacillus popilliae, B. thuringiensis 
and B. moritai—have been developed into com- 
mercial insecticides. 6. popilliae is found and 
produced only in the larv'ae of Japanese beetles. 
The other two species can be produced by con- 
ventional fermentation techniques. They have 
been useful because they foi'm spores that can 
he mass-produced easily and are stable enough 
to he handled commercially. The actual sub- 
stances that cause toxicity to the insect ai'e tox- 
ins synthesized by the microbes. 
(ienetic engineering should make it possible 
to construct more potent bacterial insecticides 
by increasing the dosage of the genes that code 
foi' the synthesis of the toxins involved. Mix- 
tures of genes capable of directing the synthesis 
of v arious toxins might also he pi'oducefl. 
Constraints on biological production techniques 
The chief impediments to using biological 
production technology are associated with the 
need for biomass.^ They include: 
• competition with food needs for starch and 
sugar; 
• cyclic availability; 
• biodegradabilitv and associated storage 
problems; 
• high moisture content for cellulosics, and 
high collection and storage costs; 
• mechanical processing for cellulosics; 
• the heterogenous nature of cellulosics (mix- 
tures of cellulose, hemicellulose, and lig- 
nin); and 
• The need for disposal of the nonferment- 
able portions of the biomass. 
For food-related biomass sources, such as su- 
gar, corn, and sorghum, few technological bar- 
riers exist for conv ersion to fermentable sugars; 
but subsidies are needed to make the fermenta- 
tion of sugars as profitable as their use as food. 
For cellulosic biomass sources such as agricul- 
tural wastes, municipal wastes, and wood, tech- 
nological barriers exist in collection, storage, 
pretreatment, fermentation, and waste disposal. 
In addition, biomass must always be trans- 
formed into sugars by either chemical or en- 
zymatic processes before fermentation can 
begin. 
■Energy Emm Biological Processes, op. oil. 
A second major im|)ediment is asso('iat(’d 
with the purification stage of [iroduction. Most 
chemical products of fei'inentation are pixxsc'nt 
in extremely dilute solutions, and concentrating 
these solutions to recovei’ th(' desiixul product is 
highly energy-intensive. Problems of technologv' 
and cost will continue to make this stage an im- 
portant one to improve. 
The developments in gi'iK'tics show gi’cat 
promise for creating moix* versatile micio-orga- 
nisms, hut they do not by themsc'lv cs pi’oduce a 
cheaper fuel or plastic. Associatc'd technologies 
still require more (?ffici(>nt f(M'mentation facil- 
ities and product S(q)ai'ation proc('sses: mi- 
crobes may producer mok'cuU's, hut they will 
not isolate, purify, concc’Uti’ate, mix, or package 
them foi' human us(v 
Fhe interaction hetwc'en genetic engineering 
and other technologi(>s is illustrated by the 
problems of pioducing ethanol by fermenta- 
tion. Fhe cas(^ study prc'sc'iiled in appendix ID 
identifi(!s those ste|)s in the hiomass-lo-elhanol 
scheiiK? that mu'd t(U'hnological improvements 
before the; |)i'oc(?ss can become ecomunicaf 
Cicnetic (MigiiKM'iing is expected to redui c 
costs in many pi'oduction slj'ps for certain 
ones— siK'h as the pretreatmeni of the hiom.iss 
to make it fermentable— gi'iielics will |)rnh.ihlv 
not play a role: physical and chemic.il lechnol 
ogies will he responsible for tin* gre.ilest ad- 
vances. Foi' otiKM's, such as distillation ^jenelic 
