2i4 SECTIONAL ADDRESSES 



later work (191 7) Currie showed that almost any culture of Aspergillus 

 niger on a concentrated sugar solution will produce more citric than 

 oxalic acid. He selected a strain of A. niger in which the lag between total 

 acidity and oxalic acid production was greatest and by appropriate sugar 

 concentration devised a method of inhibiting oxalic acid formation. The 

 process was patented. Sucrose is used in solution with the addition 

 of the necessary salts. In two to four days there is a continuous felt 

 of mycelium, and formation of citric acid begins. The fermentation is 

 complete in ten days, the solution is drained off and the mycelium pressed. 

 The amount of acid produced is about equal to half by weight of the sugar 

 used. It was recently stated that a certain American firm, in order to 

 supply the colossal amount of calcium citrate required by the American 

 cheese industry alone, is maintaining nine acres of mycelium of Aspergillus 

 niger in constant commission. 



Citric acid occurs in the juices of many fruits and formerly was 

 obtained commercially wholly from lemon, lime and bergamot by pressing 

 the fruit and concentrating the juice. It is exported either as concentrated 

 juice or as calcium citrate formed by running in chalk and water or 

 calcium carbonate. The chief exporting country in Europe was Italy. 

 An export duty was placed on calcium citrate by the Italian government, 

 and there was a manufacture tariff imposed by some countries : conse- 

 quently the juice was utilised on the spot for the production of citric acid 

 or the concentrated juice was exported. It is of interest that in 1929 

 it was stated in America that there would probably be a shortage of 

 citric acid in England because of the tendency to improve the qualities 

 of Sicilian lemons to meet the demand for higher grade fruit for export. 

 It was overlooked that four years previously a British patent had been taken 

 out by A. Fernbach and J. L. Yuill for commercial production by using 

 dark-coloured Aspergilli. There are numerous patents for the production 

 of citric acid by means of fungi and the processes are used on a large 

 commercial scale in England, Belgium, America and Japan. It is no longer 

 considered worth while to attempt further use of fruit juice in new areas. 



M. Molliard in 1932 demonstrated gluconic acid as a product of fer- 

 mentation by Aspergillus niger, and later worked out the conditions for 

 the formation of oxalic, citric and gluconic acids. In 1924 W. Butke- 

 witsch found a strain of A. niger which, in the presence of calcium carbon- 

 ate, yielded gluconic acid almost exclusively. Three years later O. E. 

 May, H. T. Herrick, C. Thom and J. N. Currie made a comparative study 

 of fungi including species of Aspergillus, Penicillium, Monilia and Mucor. 

 No species of the last two produced appreciable amounts of gluconic acid, 

 but several species of Aspergillus and Penicillium did so, the most 

 productive of which were the Penicillium luteum-purpurogeneum series, 

 particularly P. purpurogeneum var. rub rise lerotium. Herrick and May in 

 1929 patented a process for the production of gluconic acid from sugars 

 and starchy substances by fermentation with Penicillium citrinum, P. 

 divaricatum and P. luteum-purpurogeneum. Following on this several 

 workers showed that there was increased production when the mould 

 growths were submerged. Herrick and May in collaboration with A. J. 

 Moyer and P. A. Wells found that growing Penicillium chrysogenum 



