526 ENZYMES DECOMPOSING SACCHARIDES. 



hydrocyanic acid, oil of bitter almonds, and d-glucose by the aid 

 of yeast maltase, HILL (III.) became convinced of the existence 

 of a second sugar, which he named revertose, associated with 

 (Fischer's) isomaltose. On purification, this revertose, or rever- 

 tobiose, forms strongly hygroscopic, crystalline incrustations, with 

 a specific rotatory power of about a D <= +91.5? and a reducing 

 power equal to only about 47.5 per cent, that of maltose. 

 Revertose needs closer investigation. Perhaps its origin is due 

 to the invertase present in yeast extract. Attention may again 

 be directed here to the circumstance that enzymes, in addition to 

 the possession of hydrolytic or degradation properties, are also 

 able to effect the synthesis of bodies of higher molecular weight, 

 yeast maltase not being alone in the exhibition of this power. 



329. Melibiase. 



A polysaccharide known by the names melitose, gossypose, 

 melitriose, and raffinose, with which we shall become more fully 

 acquainted in 332, can be hydrolysed, by the moderate influence 

 of dilute acids, to two sugars, one of them being the well-known 

 d-fructose, whilst the other is a disaccharide with the formula 

 C lt H M O n , and to which the name melibiose was given by 

 SCHEIBLER and MITTELMEIEU (II.). Raffmose can also be split 

 up into these two sugars by certain yeasts, BERTHELOT (X.), for 

 instance, having found that the action of yeast on melitose 

 produces a non-fermentable sugar, which he named eucalyn. 

 According to BA.U (XIII.), however, his subsequent reports 

 about this compound are so contradictory that they cannot be 

 utilised in connection with melibiose. In a further communica- 

 tion BERTHELOT (IV.) states that raffinose (melitriose) is com- 

 pletely fermented by good yeast, but to the extent of only about 

 one-third by enfeebled bakers' yeast. RISCHBIET and TOLLENS 

 (I.) say that melitriose ferments readily and completely; but 

 LOISEAU (II.), on the other hand, states that this sugar, whilst 

 completely fermented by low-fermentation beer yeast, is only 

 consumed to the extent of one-third by high-fermentation yeast. 

 SCHEIBLER and MITTELMEIER (III.) found that commercial yeast 

 only fermented melitriose imperfectly, and that an amorphous 

 sugar, namely, melibiose, was left in the fermentation residue. 

 In contrast to these experiments, BAU (XIII.) demonstrated that 

 pure cultures of low-fermentation yeasts ferment melitriose 

 completely, whereas those of high-fermentation yeasts effect the 

 separation of a sugar (melibiose) which remains unaltered. This 

 worker (XXVII. and XVI.) then prepared large quantities of 

 crystallised melibiose, both by the physiological and chemical 

 methods, for particulars of which the reader is referred to the 

 original treatise. As was found by TOLLENS and his colleague 

 (VI.), and also by SCHEIBLER and MITTELMEIER (II.), this 



