MELIBIASE. 527 



disaccharide is split up by the energetic action of acids into two 

 simple sugars, cZ-glucose and d-galactose. Hence it contains the 

 same components as lactose ( 330), but in a different state of 

 chemical combination. According to BAU (XIII. and XV.), 

 mineral acids and oxalic acid alone are suitable for the acid 

 hydrolysis. 



Whereas, like lactose, melibiose is only hydrolysed with 

 difficulty by acids, it is readily split up by a yeast enzyme. After 

 BAU (XIII.) expressed the opinion, in 1894, that melibiose is not 

 fermentable direct, but must first be decomposed into its com- 

 ponents, cZ-glucose and d-galactose, E. FISCHER and P. LINDNER 

 (II.), as well as BAU (XII.) himself, working independently in 

 the following year, detected in low-fermentation yeast an enzyme 

 capable of effecting this transformation, and to which Bau gave 

 the name melibiase. 



Since the occurrence of melibiase in certain Saccharomycetes 

 can be utilised as an important chemical means for the differentia- 

 tion of groups of yeasts, we will now proceed to observe the 

 general characteristics of this enzyme, a knowledge of which 

 facilitates recognition of the value of diagnosing races of yeast on 

 the basis of the action of this enzyme. 



Melibiase which, according to E. 0. von LIPPMANN'S (IV.) 

 proposal, should be termed melibio-glucase is said by FISCHER 

 and LINDNER (II.), and also by BAU (XIL, XXVI., XXVII.), to 

 be somewhat sparingly soluble in water. The optimum tem- 

 perature at which it decomposes melibiose into one molecule of 

 cZ-glucose and one molecule of (Z-galactose, according to the 

 equation C 12 H 28 O n + H 2 = C G H 12 6 + G 6 H 12 6 , is 50 C., though a 

 considerable proportion of the disaccharide is split up at much 

 lower temperatures. The destruction temperature is 70 C., 

 though, on the other hand, as ascertained by FISCHER and 

 LINDNER (!!.)> melibiase will stand desiccation. According to 

 BAU (XXVI.), low-fermentation yeast that has been dried at 

 3~37 ^* ma y be heated to 100 C. for eight hours, or to 1 10 C. 

 for five hours, without injury to the enzyme ; and yeast dried in 

 the above manner will retain its enzymatic activity for 5^ years. 

 In this respect, melibiase has the same power of resistance as 

 invertase. 



As regards the action of chemical agents, melibiase in yeast is 

 destroyed by the influence of oxalic acid i per cent., sulphuric 

 acid i and 0.5 per cent., hydrochloric acid 0.91 per cent., sodium 

 hydroxide i per cent., silver nitrate o.i per cent., mercury 

 chloride o.i and 0.02 per cent.; a more or less enfeebling effect 

 being produced by acetic acid i per cent., oxalic acid 5 per cent., 

 sulphuric acid 0.2 per cent., sodium carbonate i per cent., sodium 

 hydroxide 0.5 per cent., silver nitrate 0.02 per cent., and alcohol 

 95 per cent. (vol.). Slight injury is caused by oxalic acid 0.2 per 

 cent., and tartaric acid 4 per cent. 



VOL. ii : PT. 2 2 L 



