Kinetics of citric acid fermentation from n‐paraffins by yeasts

In this work, yeast of the genus Candida was screened by means of shaken‐flask and jar fermentations. Two strains, Candida lipolytica Cooper and ATCC 8661, were selected. Their citric acid productivity was 0.79 and 0.67 g g −1 of n ‐paraffins consumed, respectively, and their citric: total citric and isocitric acid ratios ranged from 0.82 to 0.93, respectively. The experimental results (cell growth and total citric and isocitric acid formation) were described by using an unstructured kinetic model which has been proposed previously (standard error was less than 10%). Moreover, each independent kinetic parameter was correlated with the aeration rate of the culture medium by means of empirical regressions. Aeration of the culture medium showed a large influence on the product yield. For instance, the strain C. lipolytica Cooper exhibited the highest productivity among the examined strains, associated with the largest air consumption.