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liquid condition by the stations, e.g., by that in Geisenheim and by the fermentation laboratory at Klosterneuburg; the flasks contain as much yeast as is produced in 0.5 to 2 litres of culture liquid.

The Geisenheim station has given the following directions for the use of this pure culture yeast: The flask with the pure culture ought not to be more than two weeks old at the very most. Some days before the beginning of the actual vintage, about 12 litres of freshly prepared, not fermenting must from good, ripe, sound grapes are allowed to boil for about five minutes, being skimmed carefully meanwhile, and then allowed to cool down to the temperature of the room, the pot being covered. After cooling, the contents of the yeast flask should be poured into the must, the flask washed out several times with must, and the pot securely covered again, and placed away in a dust-free situation at the temperature of the room, until the must, after two to three days, exhibits violent fermentation. The must thus brought to fermentation is then put into the fresh must to be fermented, the quantity of which depends on the conditions at the time.

The selection of the pure yeast is of the highest importance in the preparation of sparkling wines. It affords the certainty that the after-fermentation under the extremely difficult conditions obtaining proceeds unaided, which was formerly more or less accidental and often caused the loss of large sums of money; the use of pure yeast further renders it possible to choose such yeast races as will produce little turbidity of the wine in bottle in spite of vigorous fermentation, as they separate easily and remain clinging to the cork.

The use of selected yeast races has also proved of value in the preparation of sweet wines. Its value lies chiefly in the fact that, by the aid of a yeast which is equally

vigorous to resist and to ferment in a high concentration of sugar and alcohol, wines may be produced with certainty which contain always the same amount of alcohol. A further advantage is that these wines are ready sooner, and are finer toned and preserve better than those spontaneously fermented. W. Seifert has the merit of having first made researches in practice on this subject, and of having introduced the pure culture method into this branch of wine production in the large businesses in Austro-Hungary.

The Pure Culture System in the Manufacture of Cider. The employment of selected pure yeast in the manufacture of cider is no less important than in wine manufacture. Besides the above named, Jörgensen, Kayser and Nathan have worked specially at this subject. The procedure is the same as in the preparation of wine. The results are also very satisfactory here, and ciders prepared by means of pure wine yeasts assume a more or less vinous taste and smell.

The Pure Culture System in the Manufacture of Spirit and Pressed Yeast.-The credit of bringing the pure culture system into general recognition in spirit manufacture is due to the station in Berlin. The yeasts prepared by P. Lindner (Races I and II., especially the latter) are employed in numerous distilleries and have given good results.

During the last few years the principles of race selection and pure culture have been applied in the preparation of a lactic acid bacterium for use in the above-mentioned industry; a mass culture from this bacterium is used for souring in order to prevent the injurious butyric acid fermentation. The first to introduce this pure culture into practice was Fr. Lafar. The use of lactic acid bacteria for souring the yeast mash has been considered a necessary evil by all the leading technologists. Recently, Wehmer

has attempted to use lactic acid directly instead of the bacteria. A commercial lactic acid, not absolutely pure, can now be prepared somewhat inexpensively and he has obtained good results with it in practice as a souring material.

Finally, the pure culture system has been applied in recent times in the manufacture of pressed yeast. The Berlin station has been especially active on this subject and the use of Race V., there isolated, has spread to a great extent.

Other yeast species and races applicable to the manufactures mentioned have been isolated in the technical fermentation laboratories to be found now in every country.

SECTION III.

THE MICRO-ORGANISMS OF MOST IMPORTANCE IN

THE FERMENTATION INDUSTRY.1

THE micro-organisms to be described now are partly useful, partly disadvantageous to the alcohol fermentation industry; their importance is therefore of widely different character. They all belong to that branch of the plant kingdom called fungi. The fungi are divided into two large groups: true fungi (Eumycetes) and fission fungi (Schizomycetes). The first of these two groups is divided into that of the alga fungi (Phycomycetes) and that of the higher fungi (Mycomycetes). Of the numerous fungi belonging to the phycomycetes only a single group comes to be considered here, namely, that of the Zygomycetes, and in this only the family of Mucorace.

Among the mycomycetes we shall refer partly to the sac fungi (Ascomycetes), taking representatives of the four orders, the gymnoascer with the family of saccharomycetes, the perisporace with the family of aspergilleæ, the sphæriaceae with the family of sphæries, and the discomycetes with the family of pezizacea-partly to a large group of fungi, the imperfect fungi (Fungi imperfecti), of no less importance, but which cannot yet be classified;

A bibliography is given at the end of the book.

2 We refer those wishing a more detailed description of the fungus system and the general morphology and physiology of fungi to Zopf's Handbuch der Pilze.

170

they are in all probability only stages of development of other forms of fungi.

A review of the systematic connection of the microorganisms to be described here may be made by aid of the classification given on page 173.

I-TRUE FUNGI (EUMYCETES)

is the name given to those fungi of which the vegetative organ is a mycelium. This consists of long threads which possess growing points and exhibit true branching. The first division is distinguished by this means from the second, which contains the fission fungi.

1.—Alya fungi (Phycomycetes).

The whole mycelium consists as a rule only of one single, very much branched cell. Septa only appear under special conditions, and first appear normally when fructification begins. Endogenous spores are formed in sporangia. The only group belonging to this division which we will consider here is that of the

Zygomycetes.

Multiplication takes place in these fungi partly by means of spores in sporangia, partly by means of the socalled zygospores, and in some forms by budding, by gemmae (chlamydospores) and by conidia.

Mucoracea.

The spores develop from the mass of plasma in the interior of the sporangium, a part of the plasma being left which swells by taking up water. This happens as soon as the spores are ripe, and the wall of the sporangium bursts, setting free the spores. These fungi can propagate themselves not only by means of endospores, but also by

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