Abstract

The high cost of culture media and their import are limiting factors in the production of citric acid. Therefore, the current challenge is to find inexpensive ingredients to create culture media that ensure high yields. More than 80% of citric acid is microbiologically produced. The study aims to investigate the possibility of using soybean molasses to intensify the synthesis of citric acid by Aspergillus niger. In this study, the A. niger strain (F-1270) was investigated for its ability to synthesize citric acid under conditions of modification of the nutrient medium with a carbohydrate-containing component (soybean molasses). During the research, the method of deep cultivation of A. niger in modified nutrient media was used. High-performance liquid chromatography was used to study the effectiveness of the process. Results showed that the studied strain of A. niger can actively grow and produce citric acid in a nutrient medium containing soybean molasses as a carbohydrate source. During the optimization of the biosynthesis process, the recommended values of technological parameters (duration 7 days, temperature 36.0°C, pH 2.0, and content of soybean molasses in the medium 20.0 g/L) were determined at which the yield of citric acid was 49.8 g/L, which is 18% higher than the citric acid yield (42.14 g/L) obtained using a classic culture medium (temperature 26°C, duration 7 days, pH 4.0, sucrose concentration 30.0 g/L). To increase citric acid productivity, it is necessary to improve the performance of A. niger strains by classical mutagenesis and selection.

Key words: Soybean molasses, Citric acid, Microorganisms, Aspergillus niger, Cultivation.