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been described in the last few years we will mention here among others :
Bacterium oxydans, Henneberg (Bact. aceti, Zopf).—This species is distinguished from Bact. aceti of Hansen described above, by having, as shown by Zopf and Henneberg, a swarming state; it was isolated from a bottom fermented beer from Halle.
Further, Beijerinck mentions a species which he calls Bact. aceti, and which he states to be the active species in quick vinegar manufacture. It is distinguished by forming a film on artificial nutrient liquids; this property, held in common with other species, is, however, not permanent in this species, and may be lost after a previous cultivation on solid nutrient media. All gradations of film development are presented here. Further, it liquefies beer gelatine containing cane sugar, this being due, according to Beijerinck, to the inversion of the sugar.
To what extent Beijerinck's Bact, aceti is the acetic bacterium of quick vinegar manufacture is, however, not established. Rothenbach found that the active bacteria of the process named are not in a condition to form a film. The loss of this power of film formation rests, in his opinion, on the circumstance that they are never allowed the opportunity of film formation in practice, because the mash is in continual motion. According to Rothenbach the quick vinegar bacteria are acclimatised forms. Some of them closely resemble Bact. aceti, Hansen, and can furnish vinegar containing a high percentage of acetic acid from a mash containing little nutrient substance and a high percentage of alcohol, in the Schützenbach acetifiers.
Of other acetic acid bacteria the following may be mentioned :
Bacterium Xylinum, A. J. Brown.-The gelatinous substance is cartilaginous, and furnishes the cellulose reaction with iodine and sulphuric acid, i.e., a blue colour. This species also occurs in the acetifiers of the quick vinegar process. Further, the following is described by Henneberg :
Bacterium acetigenum, which was isolated from the vinegar of & quick vinegar manufactory. It yields a cellulose reaction under certain conditions, and has especially intense power of swarming; Bacterium industrium also has a swarming state.
Several species have likewise been described under the generic name Termobacterium, as for example:
Termobacterium aceti, Zeidler, which is illustrated in Fig. 135 and which possesses a long flagellum; further
Termobacterium lutescens, Lindner, which renders beer turbid and gives rise to a celery odour in it.
We will mention still a few more Bacterium species :
Bacterium vermiforme, Marshall Ward, forms cells which measure 0:5 to 50 u long and 0:5 u broad. The gelatinisation of the cell wall with this species consists in the loosening of the strongly swollen outer layer of the cell membrane whereby the cells are enclosed as in a capsule. Together with the Saccharomyces pyriformis mentioned on p. 261 it forms the so-called ginger beer plant.
Bacterium termo, Cohn, is a collective expression for motile bacteria occurring in decomposing substances. According to Cohn's description it is a feebly fluorescent, strongly motile, short, ovate rod; but which of the numerous putrefactive bacteria is thus indicated cannot be determined.
Windisch considers that the cause of the so-called cellar flavour, by which is understood usually a raw, musty, damp taste in the beer, is undoubtedly to be looked for in the contamination of the wort during cooling, as the beer sometimes remains too long in the coolers during the warm summer months, and is, in consequence, infected by one of the bacteria belonging to the Bact. termo group.
They thrive well in hopped wort, but cannot live associated with yeast.
Most of the species included in the genus Bacillus, Cohn, form endospores. They can be classified in various groups according to their physiological activity.
Slime-forming Species. Bacillus viscosus I, and II., van Laer, were isolated from ropy beers. Both form rods with a length of 1.6 to 2:4 u and a breadth of 0.8 m; they are usually isolated, not infrequently, however, in pairs. I. forms on the surface of wort slimy, yellowish islands which appear to branch downwards. They give rise, in consequence, to a slimy covering containing bubbles, which result from the evolution of carbonic acid. II. does not form a slimy covering. The carbonic acid production and viscosity are less. The wort becomes darkbrown and a peculiar odour is evolved. A solution of 3 grams of saccharose and 1 gram of peptone in 100 cc. of water is rendered ropy and viscous by I., while II. only causes turbidity and carbonic acid evolution. A higher amount of sugar is prejudicial to the development of these bacteria, for which reason, therefore, lightly fermented beer is comparatively seldom ropy. The optimum temperature for their development is 33° C. The bacteria are frequently found in water analyses.
Bacillus viscosus III., L. Vandam, forms rods which are 2:0 u long and 0.7 u broad; they usually occur isolated ; sometimes they are joined in chains of two or three members. This species was found in English beer; the ropiness is conditioned by the presence of sugar; air is necessary for the development of the species.
Bacillus viscosus vini, Kramer, makes white wine viscous in the absence of air. It forms rods 2 to 6 u long and 0:6 to 0:8 u broad: these are often joined in manymembered chains.
Lactic Acid-forming Species. Mention has been already made of the discovery of lactic acid bacteria by Pasteur, of their importance in distilleries, and of their recent introduction into the latter in the form of pure cultures.
The first to isolate a pure lactic acid bacterium for the above purpose was, as has been said, F. Lafar. The species isolated and applied by him was Bacillus acidificans longissimus, Lafar, the cells of which are 2:5 to 25 u long and about 1 u broad.
Bacillus acidi lactici, Hueppe, consists of immotile rods which are 1.0 to 17 u long and 0:3 to 0:4 h broad; they are frequently connected in pairs, rarely in four-membered chains.
This bacillus is aërobic and does not liquefy gelatine. It loses its souring power if it is cultivated for a long time on
a sugar-free nutrient medium. As a result of seeding this species in wine, Kramer produced “ Zickenwerden” (lactic acid sharpness).
Saccharobacillus Pastorianus, van Laer, is responsible for that disease known as the “ turning” of beer. Pasteur made the discovery that the disease is caused by bacteria. The species thrives best on malt extract-agar with a little alcohol added ; this medium should be used when it is desired to obtain a pure culture. It develops in beer only when the latter contains a small amount of hop extract. According to van Laer it readily ferments saccharose (without inversion), maltose and dextrose, but lactose only with difficulty. Lactic acid, ethyl alcohol and small amounts of acetic and formic acid are found in the fermentation. Its
Fig. 146.-Lactic Acid Bacteria.
developinent in beer is prevented by over 7 per cent. of alcohol.
Butyric Acid-forming Species. It has been stated that Pasteur discovered a butyric acid bacterium which he named Vibrion butyrique ; later it was shown that this fermentation is caused by many species, which have already been alluded to as the cause of much harm in breweries.
Clostridium butyricum, Prazmowski (Bacillus amylobacter, van Tieghem), probably includes several species. The form described by Prazmowski (Figs. 134 and 137) consists of rods 1 u broad, of which the young individuals contain a substance granulose which, however, is only formed if the