PBODUCTION OF PINK SAUERKRAUT BY YEASTS 261 



iron citrate and iron ammonium citrate also favored pigment 

 production. The manganese salts apparently promoted growth 

 but did not bring about an increase in the pigment formation. 



Sugars. In order to overcome as much as possible the break- 

 ing down of the sugars from the high heat, concentrated solutions 

 of sugars in water were sterilized and added to the culture me- 

 dium when cool. The yeast medium contained the following 

 constituents : 



Ammonium sulphate 3.0 grams 



Asparagin 1.5 grams 



Dibasic potassium phosphate 2.0 grams 



Calcium chloride 0.25 gram 



Magnesium sulphate 0.25 gram 



Sugar 20.0 grams 



Agar 15 grams 



Water 1000.0 cc. 



Threa sugars were studied; xylose, glucose and maltose in 2 

 per cent solutions. Each strain of yeast was grown in triplicate 

 on agar slants, containing each sugar, and these cultures were 

 incubated at 20° to 22°C. At regular intervals, usually of 1 

 week each, these cultures were examined for rate of growth and 

 pigment production. 



All three strains showed by far the most rapid growth in the 

 glucose medium, with maltose next in order, and xylose last. 

 The decided difference between growth and pigment formation 

 is brought out in a striking manner from the results of this test. 

 Without exception the easily fermentable sugar, glucose, gave 

 a profuse growth and only a trace of pigment. Somewhat 

 similar results were obtained with maltose although a pale pink 

 was noted. In the presence of xylose these yeasts grew slowly 

 but produced a decided pink color. From these results it is 

 clear that the sugar, xylose, which is fermented only with difficulty 

 is the best one of the three for pigment production. After 

 thirty days the glucose cultures entirely lost their color while 

 the other cultures became a deeper pink. Our results agree 

 with those of Grosbusch, who foimd that the best color was 

 obtained in the case of the non-fermentable sugars, arabinose 

 and raflRinose. 



