476 ENZYMES OF YEAST. 



results, and must therefore be regarded as unreliable and defective 

 in principle, it revealed a noteworthy fact, namely, that the yeast 

 treated in this way was rendered more efficient as a fermentative 

 agent than it had been previously. This was confirmed by 

 R. ALBERT (II.), by preparing and comparing the effect of 

 expressed juice from samples of yeast before and after regene- 

 rative treatment. Additional confirmation was supplied by 

 E. BUCHNER and A. SPITTA (I.), on repeating the experiment, 

 acetonised permanent yeast being found more advantageous than 

 yeast juice. From these results it seems probable that the stock 

 of alcoholase in the yeast cells is low during the period when 

 the " head " on the fermenting wort is most abundant, the 

 alcoholase being apparently destroyed as it is formed, and not 

 accumulated. After the yeast has been stored at a temperature 

 of o C. the fermentative power is increased by 21 per cent, in 

 three and a half hours, and 1 7 per cent, in twenty hours. It 

 has also been found that yeast stored under ice water for twenty- 

 four hours does not show any increase or diminution in the 

 quantity of alcoholase present. 



According to E. BUCHNER (X.), regenerated yeast is not that 

 which contains a large store of alcoholase, but such as is capable 

 of producing this enzyme quickly. If the yeast possessed a high 

 initial fermentative power, one can hardly expect any increase 

 from regeneration and storage. The product furnished by re- 

 generation with a 20 per cent, solution of sugar was not par- 

 ticularly good in comparison with that resulting from the use of 

 an 8 per cent, solution. The addition of i per cent, of asparagin to 

 Hayduck's solution containing no nitrogenous matter led to a 

 slight diminution in the alcoholase content of the regenerated 

 yeast, without any subsequent recovery during storage. Accord- 

 ing to the more recent researches of LANGE (III.), however, the 

 fermentative power of yeast juice can be increased as much as 

 ninefold if the yeast, before trituration, be immersed in a 

 solution of saccharose containing asparagin as the chief adjunct. 

 From this it appears that asparagin favours the production of 

 alcoholase in the living cell. Further experiments on this point 

 are highly desirable. 



Whereas, in the experiments with yeast juice, the stability of 

 the alcoholase was found to be very low, the fermentative power 

 remained practically unimpaired at the end of twelve months in 

 the case of specially well-dried juice (see p. 465). According to 

 ALBERT, BUCHNER and RAPP (I.) a similar result was obtained 

 with acetonised permanent yeast, the fermentative power of 

 which decreased only by 10-19 P er cent - at * ne en ^ of six 

 months' storage in tightly stoppered bottles at room temperature. 

 Possibly the tendency toward loss of germinating power could be 

 still further prevented by diminishing the content of water. 



BUCHNER (III.) attributes the diminution of fermenting 



