MICROBES man's MIGHTY MIDGETS 37 



for its efficient and economical production. Their success hinged upon com- 

 parative studies of different mold strains together with unprecedented at- 

 tention to nutrient composition and environmental conditions. This acid is 

 now available commercially. It represents a most attractive ingredient for 

 the production of crystal-clear plastics. 



The production of acids other than lactic and acetic by bacteria has been 

 amply demonstrated, and for some of these, efficient production methods 

 have been worked out by Lockwood, Stodola, and others. Included among 

 these are the following: 5-keto gluconic acid, produced by Acetobacter sub- 

 oxydans; 2-keto gluconic acid, produced by Pseudomonas fluorescens; a-keto 

 glutaric acid, produced by P. fluorescens when the fermentation is allowed 

 to proceed beyond the 2-keto stage; maltobionic and lactobionic acids, pro- 

 duced from maltose and lactose through the oxidation of these sugars by 

 P. graveolens; and pentonic acids, produced by the oxidation of various pen- 

 tose sugars by species of Pseudomonas. 



VITAMIN BIOSYNTHESIS 



Another area of important microbial biosynthesis is found in the pro- 

 duction of vitamins. Almost twenty years ago two French microbiologists, 

 Raffy and Fontaine, reported riboflavin, or vitamin B2, to be produced by 

 a fungus, Eremothecium ashbyii, which was responsible for serious boll dis- 

 eases of cotton, particularly in Egypt and Sudan. Much interest was shown 

 in this discovery, for the essentiality of riboflavin in the nutrition of animals 

 had been clearly demonstrated. At that time, however, there was no known 

 means of producing it. Unfortunately, also, this discovery had been re- 

 vealed in Europe shortly before the beginning of World War II and no 

 accessible culture of Eremothecium had been received in this country at the 

 time communications with most of Europe were cut off. A closely related 

 organism, Ashbya gossypii, however, was known from Guillermond's work 

 to produce limited amounts of this vitamin, and a culture of this fungus was 

 contained in some of the collections in the United States. William J. Robbins, 

 at the New York Botanical Garden, had employed this latter fungus for the 

 assay of biotin in his basic and highly important studies on the nutrition of 

 many fungi and other microorganisms. The fungus in question had been 

 variously classified as a yeast and as a mold. For this reason it was of special 

 interest to L. J. Wickerham, zymologist of the Northern Regional Labora- 

 tory, who obtained a culture from Robbins. Subsequent to this, Wickerham 

 noted a yellow sector in one of his cultures, and upon re-isolation and 

 examination of this pigmented growth he observed the presence of striking 

 yellow crystals within the mycelium of the fungus. This proved to be ribo- 

 flavin. Careful attention by Wickerham and his associates to the composi- 

 tion of substrates and the conditions under which the fungus was propa- 



