Appendix l-D — The Impact of Genetics on Ethanol — A Case Study • 303 
ogies that stabilize and presen e nutritive value. The 
second approach is to increase the functionality of 
the byproducts so that more useful products can be 
developed. 
For this one can envisage clever and novel ways to 
utilize mutants to increase the value in a manner 
similar to those described.** ** Ethanol production 
is not compatible with producing a \ aluable byprod- 
uct. E.g., a filamentous yeast may be useful for direct 
te.xturization or fortification of an animal food but 
production of ethanol may not be suitable with such 
an organism. .-\ possible solution to this type of con- 
flict in\olves the de\elopment and engineering of 
two-stage fermentation processes. In the first stage, 
ethanol producing organisms are propagated under 
optimal economic conditions for ethanol production. 
.After the production phase is over, the organisms 
are then transferred to a second-stage reactor, 
where desirable phenotypic properties are then e.\- 
pressed. Signals for e.xpression of phenotypic prop- 
erties can be extrinsic environmental parameters, 
such as temperature, or levels of o.xygen or carbon 
dioxide, or intrinsic parameters, such as specific 
nutrient requirements. 
Thus the large-scale utilization of fermentation 
byproducts as feed or other materials will then 
become more valuable when genetic engineering can 
decrease processing costs and increase product 
'•A. J. Sinskev, J. Boudrant. C. Lee. J. De.Angelo. V. Miyasaka, C. Rha. and S. 
R. Tannenbaum, Applications of Temperature-Sensitive Mutants for Single- 
Cell Protein Production, " in Proceedings of L'.S./U.S.S.R. Conference on Mech- 
anisms and Kinetics of L’ptake and L'tUization of Substrates in Processes for 
the Production of Substances by Microbiological Means, Moscovv-Pushchino, 
p. 362. June 4-11. 1977. PB. 283-330-T. 
”J. Boudrant. J. De.Angelo. A. J. Sinskev. and S. R. Tannenbaum. "Process 
Characteristics of Cell Lysis Mutants of Saccharomyces cer\iciae." Biotech. 
Bioeng. 21:659. 1979. 
=“V. Miyasaka. A. J. Sinskev, J. De.Angelo. and C. Rha, "Characterization of 
a Morphological Mutant of Saccharomyces cer\isiae for Single-Cell Protein 
Production," J. Food Science 45:558:563. 1980. 
quality. Most of these types of studies remain to be 
done. However, the potential for innovative applica- 
tions is great, but such applications may not result 
because of the current lack of any Government agen- 
cy that has a sound program for funding biotech- 
nologA' research. 
Recommendations and areas in vrhich 
applied genetics should have an impact 
There has been little published research done in 
the United States on the genetic improvement of 
ethanol production processes with bacteria such as 
Zymomonas and clostridia, and only limited studies 
with yeast. In light of previous discussion, the follow- 
ing points have been identified as being the most im- 
portant and relevant in the application of genetics 
for improving ethanol-producing processes: 
• improvements on ethanol yield; 
• increased ethanol tolerance to achieve higher 
final ethanol concentrations in the fermentation 
broth; 
• increased rates of ethanol production; 
• elimination of unwanted products of anaerobic 
catabolism, that is, direction of catabolism 
towards ethanol; 
• enhanced cellulolytic and/or saccharolytic capa- 
bilities to improve rates of conversion of 
cellulose and/or starch to fermentable sugars; 
• incorporation of pentose catabolic capabilities 
into ethanol producers; 
• development of strains capable of hydrolyzing 
cellulose and starch as well as of producing 
ethanol from pentoses and hexoses; 
• improved temperature stability of micro-orga- 
nisms and/or their enzymes; and 
• improved harvesting properties of cellular bio- 
mass produced during fermentation. 
