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Abstract
Citric acid is finding new areas of usage every year, and the demand for this acid is constantly increasing. The World's production of citric acid and its sodium salt was about 300-350 thousand tons in 1982 and was predicted not to meet the demand in the mid-eighties.
Citric acid is traditionally produced in a batch culture fermentation process using a fungal strain of Aspergillus niger. The two largest producers in the United States are Charles Pfizer, Inc. and Miles Laboratories, Inc.
Yeast has been investigated in the literature as a possible citric acid producer suitable for a continuous process, with yeast having the advantage of being easily pumped and transported in a liquid based fermentation system. This work investigated the feasibility of producing citric acid continuously by fermentation of glucose with Saccharomycopsis lipolytica. The yeast was found to produce citric and isocitric acids in batch and continuous cultures working under ammonia limitation. The two acids were produced in continuous culture at rates comparable to batch culture. The effects of glucose and dissolved oxygen concentrations were also addressed in this work. Mathematical models were developed and tested for their ability to predict growth, consumption, and production rates.
