5 i2 CHEMISTRY OF ALCOHOLIC FERMENTATION. 



discovery was followed by that of other instances raised to the 

 status of fact the axiom that all the di- and poly-saccharides 

 must, in order to be capable of alcoholic fermentation by yeast, 

 be first split up into simpler sugars by special yeast enzymes 

 (which will be described later on). This circumstance forms the 

 basis of differentiation between the directly fermentable sugars 

 and the di-and poly-saccharides. The former are compounds, the 

 carbon atoms of which are arranged in a simple chain, whilst the 

 others are ether-like substances, in which separate carbon chains 

 are connected together by one or more oxygen atoms. Those 

 desirous of going more thoroughly into the study of the sugar 

 group may be referred to the works of TOLLENS (II.) and E. 0. 

 von LIPPMANN (II.). 



For the fermentable simple and compound sugars, E. FISCHER 

 (IX.) established the axiom that only such as contain a number of 

 carbon atoms divisible by 3 are susceptible of true alcoholic fer- 

 mentation by yeast. 



The first members of this group would be the trioses (C 3 H 6 3 ), 

 which do not occur in nature, but have been prepared artificially 

 and play an important part in the synthesis of sugars. According 

 to E. FISCHER (X.), alditriose or i-glycerose, is capable of alcoholic 

 fermentation ; but this is contested by WOHL (I.) and EMMER- 

 LING (VII.). This sugar is readily condensed to a compound 

 with the formula C 6 H ]2 6 , which sugar is the cause of fermenta- 

 tion phenomena in glycerose syrup. The same applies to ketotriose 

 (dioxyacetone), which is represented by the constitutional formula 

 OH.CH 2 .CO.CH 2 .OH, and was obtained by BERTRAND (VII.) in 

 the fermentation of glycerine with Bact. xylinum. According to 

 EMMERLING (VIII.), it is un fermentable, the slight fermentation 

 phenomena that make their appearance after prolonged warming 

 being attributable to the condensation of the triose into a hexose. 



Mention may also be made here of cZ-manno-nonose, a sugar 

 that is also unknown as a natural product. It has the formula 

 C 9 H ]8 9 and, according to E. FISCHER (XI.) is readily and com- 

 pletely fermented. Another sugar to be borne in mind is cZ-glyco- 

 heptose, which LINDNER (XLII.) succeeded in fermenting by 

 means of a yeast (No. 691 of the collection at the Berlin Brewing 

 Institute) from the mucinous secretion of oak-trees. Since this 

 sugar contains 7 atoms of carbon in accordance with the formula 

 CH 2 OH.(CHOH) 5 .COH this observation urgently needs confir- 

 mation, since if it be correct it disposes of Fischer's axiom respecting 

 the triplicity of the carbon atoms of fermentable sugars. 



At one time it was also thought that the pentoses, i.e., sugars 

 with the formula C 5 H 10 O 5 , including xylose and arabinose, as well 

 as rhamnose, a methylpentose C 6 H 14 O 6 , were susceptible of true 

 alcoholic fermentation by yeast. A prolonged controversy was 

 maintained on this point, on account of two circumstances : first, 

 the mixed fermentations caused by the use of impure sowings 



