PROPERTIES OF EXPRESSED YEAST JUICE. 463 



body that leaves behind, on combustion, a quantity of phos- 

 phoriferous ash. Other substances present are : ty rosin, leucin, 

 glutamic acid, nitrogenous bases, xanthin bodies, a substance 

 capable of changing sulphur to sulphuretted hydrogen and iodine 

 to hydriodic acid ; lecithin, glycerin, calcium phosphate, magnesium 

 phosphate, peculiar volatile bodies and various others. 



As was shown by BUCHNER and RAPP (V.), expressed yeast 

 juice can be desiccated without injuring any of its properties. 

 The best method is to concentrate it to the thickness of syrup 

 in a Soxhlet vacuum apparatus, after which it can be brought to 

 complete dryness by exposing it, in thin layers, to the air, at a 

 temperature of 22 0., or at 34-35 C. In the case of Munich 

 yeast juice, the fermentative power was unimpaired by this treat- 

 ment, but, according to E. BUCHNER (X.), a loss of 18-74 per 

 cent, in this respect is sustained by Berlin yeast juice. 



The most interesting feature of expressed yeast juice is the 

 enzymes it contains, which include : a fermentative enzyme, 

 a hydrolytic enzyme (decomposing maltose, saccharose and gly- 

 cogen), a proteolytic enzyme, an oxidising enzyme, a reducing 

 enzyme, one that decomposes fats, another that splits up hydrogen 

 peroxide, and a lab enzyme (see chapters Ixv. and Ixvi.). The 

 most important is the one under whose influence sugar is decom- 

 posed into alcohol and carbon dioxide. According to the recent 

 labours of BUCHNER and MEISENHEIMER (II.), lactic acid plays 

 an important part in the decomposition of sugar, and must 

 be regarded "as an intermediate product. Both these workers and 

 also MAZE (III.) attribute the fission of sugar in alcoholic fermen- 

 tation with the intermediate production of lactic acid to the 

 action of two different enzymes ; and they give the name of yeast 

 zymase to the one that decomposes the sugar into lactic acid, 

 whilst they propose the name, lactacidase, for the enzyme that 

 transforms the lactic acid into carbon dioxide and alcohol. The 

 quantitative determination of the absolute amount of fermentative 

 enzymes in expressed yeast juice has not yet been carried out. 

 The only possible means, so far, of obtaining information in this 

 direction is by comparing the fermentative value of two different 

 juices under identical conditions. All samples of expressed yeast 

 juice exhibit fermentative power, provided the yeast from which 

 they were recovered possessed any fermentative enzyme at all or 

 was able to store up such an enzyme even temporarily. The 

 fermentative power and fermentative energy, however, differ 

 considerably, and depend on the race of yeast, and on the con- 

 ditions (see 320) under which the yeast was treated for recover- 

 ing the juice. The amount of carbon dioxide furnished by 20 c.c. 

 of pressed yeast juice, in presence of 8 grms. of saccharose and 

 0.2 c.c. of toluene (as antiseptic), at the end of ninety-six hours 

 at 22 0., is 0.7-1.87 grms. According to E. BUCHNER (X.), 

 10.5 c.c. of juice and 3.5 per cent, of a 60 per cent, solution of 



VOL. ii : PT. 2 2 a 



