Citric Acid Production by Yarrowia lipolytica NRRL Y-1094: Optimization of pH, Fermentation Time and Glucose Concentration Using Response Surface Methodology

In this study, three Yarrowia lipolytica strains (Y. lipolytica NRRL Y-1094, Y. lipolytica NRRL YB-423 and Y. lipolytica IFP29) were screened for acid-production capacity and the maximum zone-area was formed by Y. lipolytica NRRL Y-1094. The strain was then selected as a potential citric-acid (CA) producer for further studies. The CA production by Y. lipolytica NRRL Y-1094 was optimized using response surface methodology (RSM) and considering three factors, comprising initial pH-value, fermentation time, and initial glucose-concentration. The highest CA-concentration was 30.31 g/L under optimum conditions (pH 5.5, 6 days, and 125 g/L glucose) in shake flasks. It has been reported that this result gives better results than many productions with shake flasks. According to estimated regression-coefficients for CA concentration, the fermentation time had the greatest impact on CA production, followed by the substrate concentration and initial pH-level, respectively. On the other hand, this study is a fundamental step in solving and optimizing the production mechanism of Y. lipolytica NRRL Y-1094, a microorganism that has not yet been used in CA production with a glucose-based medium. The results suggest that future studies can perform higher yields by optimizing other medium constituents and environmental factors.