Production of Citric Acid by Yarrowia lipolytica in Different Crude Glycerol Concentrations and in Different Nitrogen Sources

Abstract

Increased demand for biodiesel leads to an abundant amount of glycerin in the market. The value of the glycerin has much to offer in reducing the cost of biodiesel production and minimize environmental problems caused by the producers of this biofuel. Strains of the yeast Yarrowia lipolytica has the ability to grow in culture media containing glycerin stemming from the biodiesel industry and produce citric acid, which has a large industrial application. The aim of the present work was to study citric acid production by Y. lipolytica IMUFRJ 50682 using crude glycerol stemming from biodiesel industries as carbon source. It was tested different initial concentrations of glycerol and ammonium sulfate added to the culture medium. When the tests were performed to verify the influence of the concentration of glycerol used in nitrogen deficiency in the production of citric and isocitric acids, it was observed that the production of citric and isocitric acids was equal to 12.94 g/L and 6.66 g/L, respectively, in 160 h of fermentation for the test that contained 45 g/L of glycerol, showing that the strain Y. lipolytica IMUFRJ 50682 requires less carbon source to maximize the production of citric acid, generating a higher yield in terms of citric acid. In tests with the addition of ammonium sulfate to determine the influence of nitrogen source in the production of the interest, the results show that the addition of ammonium sulfate to the culture medium directs the metabolic pathway for the production of isocitric acid because it was producted only 1.46 g/L citric acid and 16.79 g/L isocitric acid in 93 hours fermentation.