Optimization of Medium Constituents for the Production of Citric Acid from Waste Glycerol Using the Central Composite Rotatable Design of Experiments

Abstract

Citric acid is currently produced by submerged fermentation of sucrose with the aid of Aspergillus niger mold. Its strains are characterized by a high yield of citric acid biosynthesis and no toxic by-products. Currently, new substrates are sought for production of citric acid by submerged fermentation. Waste materials such as glycerol or pomace could be used as carbon sources in the biosynthesis of citric acid. Due to the complexity of the metabolic state in fungus, there is an obvious need to optimize the important medium constituents to enhance the accumulation of desired product. Potential optimization approach is a statistical method, such as the central composite rotatable design (CCRD). The aim of this study was to increase the yield of citric acid biosynthesis by Aspergillus niger PD-66 in media with waste glycerol as the carbon source. A mathematical method was used to optimize the culture medium composition for the biosynthesis of citric acid. In order to maximize the efficiency of the biosynthesis of citric acid the central composite, rotatable design was used. Waste glycerol and ammonium nitrate were identified as significant variables which highly influenced the final concentration of citric acid (Y1), volumetric rate of citric acid biosynthesis (Y2), and yield of citric acid biosynthesis (Y3). These variables were subsequently optimized using a central composite rotatable design. Optimal values of input variables were determined using the method of the utility function. The highest utility value of 0.88 was obtained by the following optimal set of conditions: waste glycerol—114.14 g∙L−1and NH4NO3—2.85 g∙L−1.

Efforts to Minimise the Bacterial Genome as a Free-Living Growing System

“…To optimize more than two medium components, the combination of the statistical method Response Surface Method (RSE) and Design of Experiments (DoE) [ 79 , 80 , 81 ] is commonly used in laboratories. Plakett Burman Design (PBD) [ 82 , 83 ], Taguchi method [ 84 , 85 ], and Central Composite Design (CCD) [ 86 , 87 ] are available for DoE, and experiments can be conducted based on these designs, and optimal points can be searched by RSE based on experimental results. Despite the convenience and simple manipulation, only a limited number of components can be subjected to medium optimization with these methods.…”