Citric acid is a key biochemical in the emerging bioeconomy, to date mostly produced through fermentation by A. niger of molasses. One main issue is represented by the replacement of the molasses-based medium with less expensive and more sustainable feedstocks. Crude glycerol, a secondary product from the biodiesel industry was used without any pretreatment as substrate for fermentation by Yarrowia lipolytica DSM 8218 to produce it. The raw glycerol was retrieved from a local biodiesel production plant. The fermentation set-up was first optimized in flasks by using the Response Surface Methodology (RSM). A 3-level Full Factorial Design of Experiment was employed to investigate the impact of crude glycerol concentration and C/N ratio on citric acid yield and two N sources (ammonium sulphate and yeast extract) were alternatively tested. The optimized conditions were subsequently applied to a 2L bioreactor. The best conditions to maximize YCA were found to be: crude glycerol 33 g/L and C/N 141, which resulted in the production of 8 g/L of citric acid and in a metabolic yield of 0,27 g/g. Scale up in bioreactor indicated that the citric acid production like can be controlled and improved by adjusting the concentration of dissolved oxygen.
Conversion of crude glycerol to citric acid by yarrowia lipolytica
Albergo R.;Valerio V.;
2019-01-01
Abstract
Citric acid is a key biochemical in the emerging bioeconomy, to date mostly produced through fermentation by A. niger of molasses. One main issue is represented by the replacement of the molasses-based medium with less expensive and more sustainable feedstocks. Crude glycerol, a secondary product from the biodiesel industry was used without any pretreatment as substrate for fermentation by Yarrowia lipolytica DSM 8218 to produce it. The raw glycerol was retrieved from a local biodiesel production plant. The fermentation set-up was first optimized in flasks by using the Response Surface Methodology (RSM). A 3-level Full Factorial Design of Experiment was employed to investigate the impact of crude glycerol concentration and C/N ratio on citric acid yield and two N sources (ammonium sulphate and yeast extract) were alternatively tested. The optimized conditions were subsequently applied to a 2L bioreactor. The best conditions to maximize YCA were found to be: crude glycerol 33 g/L and C/N 141, which resulted in the production of 8 g/L of citric acid and in a metabolic yield of 0,27 g/g. Scale up in bioreactor indicated that the citric acid production like can be controlled and improved by adjusting the concentration of dissolved oxygen.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
