424 



STATE BOARD OF AGRICULTURE. 



were reinoculated with 1 cc. of a 16 day whey culture of the yeast LZ. 



but the lactic acid at this time was present in such strength that the 

 yeast did not grow and the presence of the acid eventually killed the 

 lactic bacteria. Test cultures made at the end of 04 days from the 

 mixed cultures of the lactic bacteria and the red yeast showed no 

 growth with the exception of No. 53B2 which is capable of retaining 

 its vitality and activity over long periods of time, not seeming to be 

 inllueuced b}' the amount of acid produced, therefore the survival of 

 this lactic bacterium could not be attributed to the presence of the yeast 

 or its products. 



It will also be noted that the Strains No. 2 and No. 4 in mixed cul- 

 tures with veast LZ reached an unusuallv high aciditv for ordinarv 

 lactic bacteria; both microscopical examination and plating revealed 

 only ordinary lactic bacteria and the yeast LZ present. In later ex- 

 periments, weak lactic bacteria were stimulated by growth with the 

 veast so that thev were induced to i)roduce nearlv double their usual 



t/ t. X t 



amount of acid, but this amount was never greater than that produced 

 by pure cultures of typical lactics. 

 Table VII gives the data for the duplicate mixed cultures in whe}'. 



TABLE VII. 

 Acidity of Mixed Cultures in Whey. 



♦Slimy. 



tTest cultures made at this time aod at 64 days. 



°Yeast LZ not present in these cultures. 



The difference in the four lactic bacteria in mixed culture is much 

 more marked in the whey cultures; the rise in acidity takes place more 

 quickly in No. 2 than in No. 4, and much more quickly in No. 53B2 than 

 in Bact. bulgaricum or in the typical starter bacterium. In fact, in 

 the mixed cultures of Bocf. bulgaricum growing with the three acid- 

 de.stroying yeasts, the original acidity of the whey (13°) was reduced 

 4° — 7° by the yeasts before the lactic bacteria had multiplied suffi- 

 ciently to produce a mensurable quantity of acid. Yeast LZ grew only 

 in the whey flask with Bact. buhjaricuin. The following curves are 

 illustrative "of Tables VI and VII: 



