110 • Impacts of Applied Genetics — Micro-Organisms, Plants, and Animals 
Genetics in baking; brewing; and winemaking 
The micro-organism of greatest significance 
in the baking, brewing, and winemaking indus- 
tries is common yeast. Because of its impor- 
tance, yeast was one of the first micro-orga- 
nisms to be used in genetic research. Neverthe- 
less, the surge in studies in yeast genetics has 
not been accompanied by an increase in its 
practical application, for three reasons: 
• industries already have the desired effi- 
cient strains, mainly as a result of trial-and- 
error studies; 
• new genetic strains are not easily bred; 
they are incompatible for mating and their 
genetic characteristics are poorly under- 
stood; and 
• many of the important characteristics of 
industrial microbes are complex; several 
genes being responsible for each. 
Changing technologies in the brewing indus- 
try and increased sophistication in the molec- 
ular genetics of yeast have made it possible for 
researchers to achieve novel goals in yeast 
breeding. One strain that has already been con- 
structed can produce a low-carbohydrate beer 
suitable for diabetics. (See figure 26.) 
The baking industry is also undergoing tech- 
nological revolution, and yeasts with new prop- 
erties are now needed for the faster fermenta- 
tion of dough. New strains with improved bio- 
logical activity, storage stability, and yield 
would allow improvements in the baking proc- 
ess. 
In the past, most genetic applications have 
come in the formation of hybrid yeasts. The 
newer genetic approaches, which use cell fu- 
sion now open up the possibility of hybrids de- 
veloped from strains of yeast that carry useful 
genes but cannot mate normally. 
Classical genetic research has also been car- 
Figure 26.— The Use of Hybridization To Obtain 
a Yeast Strain for the Production of 
Low-Carbohydrate Beer 
Saccharomyces 
Saccharomyces 
carisbergensis (yeast) 
Mated with 
diasticus (yeast) 
(strain 1)a 
(dextrin fermenting 
ability) 
Hybrid yeast 1 
Mated with 
Saccharomyces 
(palatabie beer) 
carisbergensis 
(strain 1) 
Hybrid yeast ii 
(palatabie beer) 
Mated with 
Wild yeast 
(isomaltose, 
isomaltotriose 
fermenting ability) 
Hybrid yeast III 
(produces diabetic 
beer) 
^Strain 1 1s a brewing yeast. 
SOURCE: Office of Technology Assessment. 
ried out with wincf v(fasts. Interestingly, within 
the past 10 years, scientists haw isolated in- 
duced mutants of witK* yeasts that haw; II an 
increased alcohol tolerance and the ea|)aeit\' to 
completely ferment grapt' extracts of unusually 
high sugar contcfiit; 2) impro\(*d sedimentation 
properties, im|)ro\ ing or facilitating separation 
of yeasts from the w incf; and ;0 improwd per- 
formance in the production of certain types of 
wines. Hybridization studies of wine yeasts 
have been actixely pursiu'd only recently. 
Progress in de\(’loping strains of y(>ast w ith 
novel properticfs is limitc'd by the lack of (Miough 
suitable approxcnl systems lor using recombi- 
nant DNA (rl)N/\) tcM'hnology. I.vcntual approv- 
al by the Kcfcomhinant l)N \ \d\ i.sory ( ommit- 
tee is ex[)(fct(ul to boost applied research lor the 
Ijrewing, baking, and w inemaking industries 
