SOME FACTORS AFFECTING INULASE FORMATION 



IN ASPERGILLUS NIGER 



V. H. YOUNG 



State University of Iowa, Iowa City, loiva 



D. EXPERIMENTAL RESULTS 

 a. Preliminary experiments 



The results of numerous preliminary experiments clearly indi- 

 cate that Aspergillus niger grows well on the culture medium 

 above mentioned in which the ordinary carbohydrates are used 

 as the source of carbon. Cultures grown on inulin appeared to 

 be slightly stimulated during the first twenty-four hours of 

 growth and came to full sporulation a few hours before cultures 

 grown on glucose, sucrose or maltose. The dry weight of the 

 mycelium formed at the beginning of sporulation of cultures 

 grown on inulin was generally slightly less than that of cultures 

 grown on equal concentrations of the sugars mentioned. Growth 

 on soluble starch was rather slow and the amount of growth 

 somewhat less than on any of the other carbohydrates, except 

 lactose, which, as Dox (1910) and others have already shown, 

 produces almost no growth unless the fungus is at first started 

 on other media and then transferred to lactose. Tests with 

 Fehling's solution of culture media containing inulin as a source 

 of carbon showed strong reducing power after the fungus had 

 grown for a day. Whether or not reducing sugars are present 

 at the beginning of sporulation appears to depend on the pri- 

 mary concentration of inulin. Up to the point where the amount 

 of inulin present was clearly in excess of what could be rapidly 

 assimilated by the fungus, the dry weight of fungus produced 

 was nearly proportional to the amount of inulin present. 



The results of preliminary experiments both with fresh mycelial 

 extracts and with the extracts of the mycelium treated as de- 

 scribed above show an abundant hydrolysis when these solutions 



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