The sticky residue dries up very rapidly in vacuo to a brittle, scaly mass, which is converted by grinding into a light yellow powder.
The filtrate was invariably found to be quite devoid of fermenting power, none of the enzyme passing through the gelatin.
Fig. 6.
Properties of the Filtered and Washed Residue.—The residue prepared as described above consists mainly of the protein, glycogen, and dextrins of the yeast-juice, and is almost free from mineral phosphates, but contains a certain amount of combined phosphorus. It also contains the enzymes of the juice, including the proteoclastic enzyme, and the hexosephosphatase (p. [54]). Its solution in water is usually quite inactive to glucose or fructose, but in some cases produces a small and evanescent fermentation. When the original filtrate or a corresponding [p061] quantity of the filtrate from boiled fresh yeast-juice is added, the mixture ferments glucose or fructose quite readily. The following table shows the quantitative relations observed, the sugar being in all cases present in excess:—
| No. | Material. | Volume. | Fil- trate added. c.c. | Boiled Juice added. c.c. | Water added. c.c. | CO2 evolved. |
|---|---|---|---|---|---|---|
| 1 | Undried and unwashed residue | 15 c.c. | 0 | 0 | 15 | 0 g. |
| 15 " | 15 | 0 | 0 | 0·035 " | ||
| 2 | 15 " | 0 | 0 | 15 | 0·024 " | |
| 15 " | 0 | 15 | 0 | 0·282 " | ||
| 3 | Undried and washed residue | 25 " | 0 | 0 | 0 | 0·4 c.c. |
| 25 " | 0 | 25 | 0 | 268 " | ||
| 4 | 20 " | 0 | 0 | 0 | 8·3 " | |
| 20 " | 20 | 0 | 0 | 90·3 " | ||
| 5 | Washed and dried residue | 1 gram in 15 c.c. | 0 | 0 | 0 | 0 " |
| 0 | 12 | 0 | 108 " | |||
| 6 | 1 gram in 25 c.c. | 0 | 0 | 0 | 0 " | |
| 0 | 25 | 0 | 364 " |
These experiments lead to the conclusion that the fermentation of glucose and fructose by yeast-juice is dependent upon the presence, not only of the enzyme, but also of another substance which is dialysable and thermostable.
Precisely similar results were subsequently obtained by Buchner and Antoni [[1905, 2]] by the dialysis of yeast-juice. One hundred c.c. of juice were dialysed for twenty-four hours at 0° against 1300 c.c. of distilled water, and the dialysate was then evaporated at 40° to 50° to 20 c.c. The fermenting power of 20 c.c. of the dialysed juice was then determined with the following additions:—
- (1) 20 c.c. of dialysed juice + 10 c.c. of water gave 0·02 gram CO2.
- (2) 20 c.c. of dialysed juice + 10 c.c. of evaporated dialysate gave 0·52 gram CO2.
- (3) 20 c.c. of dialysed juice + 10 c.c. of boiled juice gave 0·89 gram CO2.