ORGANIC-ACID PRODUCTION BY PROPIONIBACTERIUM-SHERMANII - EFFECT OF PH, TEMPERATURE AND VITAMIN-NITROGEN SOURCE

Production of propionic acid by Propionibacterium shermanii CDB 10014 was enhanced by a pH value of 6.5 and by temperatures in the range 35- 37 degrees C. Depending on the type of yeast extract, succinic acid ca n be produced in higher proportions, with decreasing propionic acid yi elds. With respect to propionic acid production, Difco yeast extract h as shown the best results when yeast extract preparations from other d ifferent suppliers were compared. To replace yeast extract by a cheape r vitamin-nitrogen source, corn-steep liquor was tested. A complete de pletion of glucose was achieved, yielding a final propionic acid conce ntration of over 35 g/l. These results are even better than those obta ined with Difco yeast extract and suggest the possibility of an econom ical process based on corn-steep liquor.