254 LACTIC ACID BACTERIA IN DISTILLING, ETC. 



the case to the natural susceptibility of the wine to infection. 

 No known remedy exists for the lactic taint in wine, but Pas- 

 teurisation may be recommended as a preventive measure. 



152. The "Turning" of Beer. 



Although the term " turning," as applied to wine, is not yet 

 clearly defined, still, in the case of beer, only a single malady is 

 understood by this definition, viz., the undesirable appearance of 

 lactic fermentation. PASTEUR (III.) made several observations 

 on "biere tournee," and traced the cause to certain fission fungi, 

 which he described as long rods i //, broad and of variable length, 

 frequently joined together in chains. For a closer investigation 

 of these we are indebted to H. VAN LAER (I.), who in 1892 

 obtained pure cultures of this ferment, and named it Saccharo- 

 bacillus pastorianus. 



The commencement of this malady in beer is evidenced by a 

 gradual decrease in the brightness of the (previously clear) liquid, 

 which finally becomes quite turbid, and gradually assumes an 

 unpleasant smell and taste. If the sample be shaken, delicate 

 waves of a fine thread-like character appear in the liquid, re- 

 sembling in appearance the fine films produced at the plane of 

 contact between two liquids of unequal densities. This appear- 

 ance is so remarkable, that it suffices of itself to characterise the 

 malady. After a time there separates out a deposit, which Pasteur 

 reproduced in Plate II. of his above-mentioned work, and which 

 consists apart from the yeast-cells, which may be disregarded 

 of a nitrogenous precipitate thrown down by the lactic acid, and 

 of single cells and chains of Saccharobacillus pastorianus. The 

 latter are the cause of the aforesaid optical phenomenon exhibited 

 when the liquid is shaken. Meat-broth gelatin is unsuitable for 

 the pure cultivation of this fission fungus, and it develops but 

 imperfectly in wort-gelatin, so that slightly alcoholised malt 

 extract agar-agar, in which the organism thrives, has to be em- 

 ployed. The re-inoculations made by Van Laer into sound beer 

 decisively proved the agency of Saccharobacillus pastorianus in 

 the production of "turning" in that beverage. It is, however, 

 incapable of developing or becoming injurious except when the 

 percentage-content of hop extract (i.e. the hop resins inimical to 

 bacteria) in the medium is small. This influence of the hop resins 

 was, however, not further investigated by Van Laer. 



As its generic name implies, Saccharobacillus pastorianus 

 ferments sugars, and especially saccharose, maltose, and dextrose, 

 which it acts upon readily, but, on the other hand, ferments lactose 

 with difficulty. Saccharose is apparently transformed without 

 inversion, since the presence of invertin could not be detected in 

 the cultures. In media containing one of these sugars the bacillus 

 chiefly produces inactive lactic acid, in addition to ethyl-alcohol 



