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

Ewelina Ewa Książek; Małgorzata Janczar-Smuga; Jerzy Jan Pietkiewicz; Ewa Walaszczyk

doi:10.3390/molecules28073268

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

Molecules. 2023 Apr 6;28(7):3268. doi: 10.3390/molecules28073268.

Authors

Ewelina Ewa Książek¹, Małgorzata Janczar-Smuga², Jerzy Jan Pietkiewicz³, Ewa Walaszczyk⁴

Affiliations

¹ Department of Agroengineering and Quality Analysis, Faculty of Production Engineering, Wroclaw University of Economics and Business, Komandorska 118-120, 53-345 Wrocław, Poland.
² Department of Food Technology and Nutrition, Faculty of Production Engineering, Wroclaw University of Economics and Business, Komandorska 118-120, 53-345 Wrocław, Poland.
³ Department of Human Nutrition, Faculty of Health and Physical Culture Sciences, Witelon Collegium State University, Sejmowa 5A, 59-220 Legnica, Poland.
⁴ Department of Process Management, Faculty of Production Engineering, Wroclaw University of Economics and Business, Komandorska 118-120, 53-345 Wrocław, Poland.

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.

Keywords: Aspergillus niger; citric acid; design of experiments; glycerol; optimization; response surface methodology.

MeSH terms

Aspergillus niger / metabolism
Citric Acid* / metabolism
Fermentation
Glycerol* / metabolism

Substances

Citric Acid
Glycerol

Supplementary concepts

Aspergillus brasiliensis

Grants and funding

The work was financially supported by a special-purpose grant from the Ministry of Science and Higher Education (Poland) related to the development of scientific specialties of young scientists and participants of doctoral studies—awarded in 2015–2017.