Abstract:
Twenty five strains of yeasts were screened. It was found that 16 strains of yeasts could grow and produce acids. Only 7 strains could ; produce citric acid by utilizing n-paraffin as a carbon source. Candida ; oleophila C-73 gave the highest yield of citric acid (29.5 g/1) in n-paraffin containing medium. The optimal compositions of production medium for citric acid fermentation by Candida oleophila C-73 contained 10% (w/v) n-paraffin (Exxpar-451), as a sole carbon source, and 0.2% (w/v) anmonium nitrate as a nitrogen source. The other important compositions were 0.01% (w/v) potassium dihydrogen phosphate, 0.05% (w/v) magnesium sulfate heptahydrate, 0.02% (w/v) manganese sulfate monohydrate, 0.1% (w/v) yeast extract and 10% (w/v) calcium carbonate. The optimal condition for citric acid production was carried out aerobically by rotary shaken at 300 rpm, 25๐c with the addition of 0.001% (w/v) 2, 4-dinitrophenol after cultivation for 24 hours. The highest citric acid production (131.5 g/1) was obtained after 6 days of cultivation.