MICRO-ORGANISMS. 145 
eleven parts of sugar; but, owing to a fall in the price of the 
natural acid, the mycological industry failed. 
The Vinegar Fermentation. 
The vinegar manufacturer has much to contend against. 
Up to a certain point he is virtually a distiller; that is to 
say, he produces alcohol from the cheapest possible source, 
and uses up most of the fermentable carbohydrates. There 
is this difference, however, and here the vinegar manufac- 
turer resembles the brewer—the fermenting mash cannot 
be acidified by lactic bacteria, nor treated with antiseptics, 
such as fluorides, since neither lactic acid nor fluorides must 
appear in the finished product. The grain which furnishes 
the starch is usually kiln-dried, and this practice, besides 
producing flavouring substances and assisting the gelatinisa- 
tion of the starch, kills off most of the moulds and bacteria 
on the surface of the grain. After saccharification and 
attenuation of the wort, a good quantity of brewers’ yeast 
is added. This is quite legitimate, for in a vinegar factory, 
where a mash is made intermittently, it is better to use 
brewers’ yeast—generally a stable substance, owing to the 
regularity of the brewing process—than to keep over yeast 
from a previous fermentation. The addition of what may 
be called an excess of yeast gives a rapid start to the fer- 
mentation, thus reducing the possible secondary bacterial 
fermentations. The fermented wort, after aération, is 
passeld into the acetifier, which contains twigs infected with 
vinegar-slime. The acetifying wort is repeatedly passed by 
pumping and sparging over the portion of the acetifier which 
contains the slimy twigs. 
It is perhaps im the preparation of these infected twigs 
that the manufacturer has the most need of selected and 
pure vinegar bacteria. Infecting the twigs from an old 
slime, which may be the home of many organisms besides 
the acetic bacteria, is neither scientifically nor economically 
correct, although, practically, it may be easy. The acetic 
bacteria are many, and, like other bacteria, they differ 
among themselves in their capacity for doing the work that 
is required of them. For example, it has been shown that 
some acetic bacteria produce three times as much acid as 
others, and that some can withstand twice the amount of 
alcohol that others can. In one respect bacteria are. like 
human beings—they must be fed; and this is notably so in 
the acetification of the alcoholic fluid. If the food con 
stituents, t.¢., the salts, carbohydrates, or nitrogenous matter, 
become exhausted, the bacteria refuse to work until pro- 
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