214 



PHYSIOLOGY OF THE FUNGI 



Table 35. Yield of Saccharomyces cerevisiae Cells Produced when Different 



Amounts of Yeast Hydrolysate Were Added to 25 Milliliters of a 



Biotin-free Glucose-Casein Hydrolysate Medium 



The amount of biotin in the original sample may then be calculated. 

 The amount of biotin in 6.25 mg. of the sample produced 32.8 mg. of 



60 



50 



«40 



S30 



©20 



10 



0.001 0002 O004 0.006 0.008 



Micrograms of biotin per flosk 



Fig. 43. Standard curve for a biotin assay using Saccharomyces cerevisiae, Gebriide 

 Mayer strain, as the test fungus. Basal medium was glucose-casein hydrolysate, 

 25 ml. per 250-ml. Erlenmeyer flask. Cultures were incubated at 25°C., agitated 10 

 min. each hour, and harvested after 72 hr. 



dry yeast cells. From the standard curve this is seen to be equivalent 

 to 0.0025 jug of biotin. The biotin content of the sample is therefore 

 equal to 0.0025 X 1,000/6.25, or 0.4 /xg of biotin per gram of sample. 



VITAMIN ASSAYS 



It is beyond the intent of this chapter to include detailed information 

 about techniques in connection with individual assays. The following 

 references are useful for entry into the hterature. Schopfer (1945) has 

 considered the philosophy underlying the use of microorganisms for 

 assay. Leonian and Lilly (1945) investigated the use of many test 

 organisms to assay the vitamin content of a single substance. This work 

 showed that widely different assay values for some vitamins are obtained 



