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from turned wines.

Kramer isolated two Micrococcus species

The bacteria of lactic acid, butyric acid and acetic acid may be mentioned as acid producers in fermented liquids. In breweries the first are especially active in the mashing stage. According to van Laer a species, Saccharobacillus Pastorianus, causes the turning of beer; the beer thereby loses its brilliancy, becomes disagreeable in smell and taste and forms a sediment; the latter consists partly of nitrogenous products which separate as a result of lactic acid production, and partly of the bacteria themselves. Bacillus acidi lactici, according to Kramer, causes the "Zickenwerden" (see p. 343) of wine. Butyric acid bacteria are responsible for a very unpleasant smell and taste in beer. They are especially injurious in the mashes in distilleries.

Acetic acid bacteria are found particularly in wine manufacture, where they occasion the tartness of the wine. When once the wine has been strongly attacked by them, and is in consequence vinegar sour, it is valueless; there is then no means of removing the evil. In brewing they are of most danger in top fermentation breweries, where the conditions for their development are more favourable than in bottom fermentation breweries. Hansen experimented in practice with Bacterium aceti and Bact. Pasteurianum in the presence of Carlsberg bottom yeasts No. 2 and No. 1. He came to the conclusion that the bacteria in question were indeed present in the finished lager beer if the infection took place at the beginning as well as at the end of the primary fermentation, but that this infection appeared neither in the fermentation cellar nor in the lager cellar. The bacteria can propagate themselves only after the lagered beer is drawn off; the beer, however, did not become vinegar sour if care was taken that the transport vessels and bottles were well closed and well filled. The same holds good

also when the bacteria are introduced into bottom fermented

beer after it has left the lager cellar. The infection generally occasioned no bad effects when the precautions named were observed. High temperature and free air access are necessary for the development of the bacteria.

Gayon and Dubourg found in wine containing mannite, a short non-motile rod which forms masses of zooglœa. It reduces invert sugar to mannite. Wine, however, is most exposed to this disease in warm climates. (As formerly mentioned, Penicillium glaucum can cause the same phenomenon.)

According to the investigations of V. H. and L. J. Veley, the disease of rum, called "faultiness," is brought about by a bacterium which these authors name Coleothrix methystes. This species is especially distinguished by its great power of resisting alcohol, the bacteria retaining life in rum with an alcohol content of 75 per cent. by weight.

Pediococcus or Sarcina species frequently occur in breweries. However, only certain of these cause harm, and these only under special conditions. It has been shown by Hansen, Jörgensen and Ant. Petersen that when certain of the species occur even in considerable amount in beer, they are without appreciable influence on its quality. These forms have been especially studied by P. Lindner (1888). According to him and other authors, some species under certain conditions occasion "sarcina turbidity". In this connection Reichard states that the disease appears when a strong afterfermentation takes place in beer inoculated with Sarcina, while equally strongly infected beer did not succumb to the disease when the primary fermentation was a strong one, so that in place of the vigorous after-fermentation, only a slight maturing took place. An addition of hops to the lager casks will, according to the same author, prevent an outbreak of the Sarcina disease.

Schönfeld has also investigated the infection of yeast by Pediococcus and Sarcina. His results are the following: Culture yeasts are susceptible to Sarcina in varying degree. Wild yeasts are more prejudicial to the development of Sarcina than culture yeasts; with favourable conditions a Sarcina acclimatised to any yeast race can spoil the beer prepared by means of this yeast; Sarcina is more anaerobic than aerobic; the virulence of Sarcina is dependent upon certain medium temperatures, an absence of air, and on motion; the multiplication of Sarcina is restricted by strongly hopping the beer, by high alcohol content and by aëration.

Kupfer seeks for the causes of the poor "head" and slight stability of beer in Sarcina infection.

S. v. Huth has recommended the employment of a tartaric acid remedy for Sarcina, in which 6 grams of tartaric acid are added in aqueous solution to every kilo of yeast. After stirring, the whole is put on one side to rest for six to twelve hours, after which the mixture is introduced into the fermenting vessel. This method must always be applied with care, and is only to be recommended when the stock yeast contains practically no wild yeast. For if this is not the case the latter develops at the expense of the culture yeast, and the result proves correspondingly unfavourable.

5. APPLICATION OF BACTERIA IN THE ALCOHOLIC FERMENTATION INDUSTRIES.

Only the lactic acid-forming bacteria are directly employed in the alcoholic fermentation industries, these being applied in distilleries in subduing butyric acid bacteria and in the "Weissbier" breweries. In breweries the yeast settles to the bottom of the dilute wort; such does not happen in distilleries, where the thick mash does not allow of this.

The pitching yeast is therefore produced by itself in special vessels. The requisite amount of nutrient liquid for this is acidified in order to prevent the development of harmful germs, such as butyric acid bacteria, which are unable to thrive in strongly acid liquids. A strong and suitable formation of acid is therefore effected by the addition of a young and vigorous pure culture of lactic acid bacteria. The latter is obtained by

starting from a trial mash of which the souring is satisfactory. The optimum temperature for lactic acid bacteria lies at about 50° C., that of butyric acid bacteria, on the other hand, at about 40° C. The sweet yeast mash is therefore kept at about 50° C., in which case only a strong growth of lactic acid bacteria develops. When the degree of acidity is sufficiently high, the lactic acid bacteria are killed by warming the mash up to 70° C., following this it is quickly cooled to 17° to 20° C., and a pure culture of a selected yeast race added. A part of the yeast produced is then taken out to be used in pitching a fresh portion of sweet mash.

As formerly mentioned, F. Lafar was the first to introduce the systematic selection of a lactic acid bacterium for this purpose. Wehmer, however, has lately attempted to suppress butyric acid bacteria with commercial lactic acid, which, according to his investigations, has given good results.

Of the remaining bacteria referred to, those of acetic acid are employed, as is well known, in the manufacture of vinegar.

SYSTEMATIC.

Ferd. Cohn showed that bacteria are plants, and set up a system based on cell form. We have seen, however, that the same species can assume various forms of growth.

For the investigation of different species, the morpho

logical and developmental characteristics are, in the first place, applied as far as possible, e.g., the shape of the cell, the presence of flagella and their arrangement, the mode of germination of the endospores, etc. Further, the forms which the growth assumes on various nutrient media, e.g., on culture gelatine, in which case it is also observed to what extent the species liquefies gelatine, if at all. The products resulting from growth are also of importance. The cultures are prepared either as streak or stab cultures, the former on the surface of the gelatine, the latter by stabbing in a thick layer of gelatine (see p. 98). Drop seeding on the surface of the gelatine is also employed. The behaviour of bacteria species with various staining methods takes a large place, especially in medical bacteriology.

The bacteria considered here can be divided into two chief groups, viz., spherical bacteria (Coccacea) and rod bacteria (Bacteriacea), by which means, on practical grounds, we retain the old classification, in which shape was the criterion, and also the older names which are generally known. The author, however, is, on this point, neither for nor against this arrangement. The classification of bacteria. is at present very uncertain, and is still subject to change, since no fixed, systematic, distinctive lines can be laid down. That the shape, moreover, is in several respects of little value as a systematic distinguishing feature follows, among other things, from what has been said in the foregoing on the polymorphism of bacteria.

I-FAMILY: SPHERICAL BACTERIA (COCCACEE).

In the isolated state the cells are spherical. Fission takes place along one, two or three planes.

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