Studies on the Production of Organic Acids by Filamentous Fungi

The purpose of this investigation was to study some of the factors which might increase the efficiency of production of acid by certain recently isolated strains of fungi. The fungi employed in these studies were made available through the courtesy of Dr. G. L. Peltier from whose collection they came. All the cultures were maintained on potato dextrose agar slants and were transferred frequently. The highest acid producers of the fungi belonged to the black Aspergilli group, the green Aspergilli ranking second on the basis of total acid produced.The latter is not, however, a good criterion in judging acid production.The yield will depend to a great extent upon the type of acids that predominate in the fermented medium, that is tricarboxylic, dicarboxylic or monocarboxylic.Of the carbohydrates used, glucose, sucrose, starch, cellulose, Diamalt, xylose, and corn cobs, sucrose was found to be the most readily available carbohydrate in the case of the black Aspergilli, while for the Aspergilli green, tan and golds, glucose was as good and in many instances better than sucrose.Low initial hydrogen ion concentration seems to favor acid production with MF 436, the optimum pH being about 3.5.The use of deionized sugar beet crowns and ferrocyanide treated crowns gave high enough yields to warrant further study. Advisor:Carl E. Georg