GLUCONIC ACID FERMENTATION 225 



search Laboratory of the U. S. Department of Agriculture, May, 

 Herrick, Wells, Moyer, and their associates, have carried out exten- 

 sive studies on the methods and apparatus which are best suited for 

 the production of this acid. 



In the original shallow-pan method investigated by Herrick and 

 May," the organism used was Penicilliwn purpurogenum var. 

 rubrisclerotium (Thorn No. 2670). With this method of production, 

 the gluconic acid yield was the best with a high concentration of 

 sugar, 20 to 25 per cent solution of glucose, and a temperature of 

 25° C. The efficiency in the conversion of sugar to gluconic acid 

 was found to be affected by the ratio of surface to volume of liquid, 

 a ratio between 0.25 and 0.30 being the most feasible. Although 

 agitation of the nutrient solution proved favorable when the con- 

 centration of the sugaif was low, it did not affect the production of 

 the acid when the sugar-concentration was high. The fermentation 

 could be carried out successfully over a wide pH range, 3 to 6.4. 

 Yields of 55 to 65 per cent were obtained in about 11 days. The 

 mold was grown on a glucose-salt solution in aluminum pans placed 

 in a sterilizable chamber. 



Since Schreyer," working with A. jumaricus, first demonstrated 

 in 1928 that the yield of this acid could be increased by agitation, 

 aeration, and the use of calcium carbonate, a number of investigators 

 have studied this technique of fermentation. With submerged 

 growths of P. chnjsogenum, aerated with filtered and humidified air. 

 May, Herrick, Moyer and Wells ^^ were able to obtain 80 to 87 per 

 cent yields in about 8 days. The temperature used was 30° C. and 

 calcium carbonate was added at the rate of 1 gram for every 4 grams 

 of glucose. In addition to glucose, salts were added to the medium 

 and nitrogen was supplied in the form of ammonium nitrate. 



Herrick, Hellbach, and May 2« have\also developed a rotary drum, 

 submerged growth method using a strain of A. niger. The advantage 

 of the rotating drum, submerged growth method (which they have 

 developed to a pilot plant scale) over the aerated and agitated, sub- 

 merged growth method was that the fermentation time could thus 

 be cut down considerably, 80 per cent yields being obtained in a little 

 over 2 days. The rotary drum apparatus is essentially a horizontally 

 mounted, hollow, aluminum cylinder closed at both ends and equipped 

 with buckets and baffles placed on the inside walls. The drum is 

 slowly rotated to keep the fermenting culture aerated and mixed. 

 A serai-continuous process has also been developed.*^ For specific 



