2-Keto-gluconate production and purification by thermotolerant acetic acid bacterium Nguyenibacter vanlangensis KKS-R1

Abstract

2-Keto-gluconic acid (2-KGA) is a pivotal intermediate in the production process of ascorbic acid, commonly known as vitamin C. The bacterium Nguyenibacter vanlangensis KKS-R1 is an acetic acid bacterium (AAB) that has been selectively screened for its ability to produce 2-KGA among twenty-five bacterial isolates at high temperatures up to 40°C. This thermotolerant property makes it advantageous for various industries. Therefore, it has garnered interest for its potential application in the production of 2-KGA and purification of the 2-KGA product. This study evaluated the production of 2-KGA by N. vanlangensis KKS-R1 using 1% gluconate as the substrate. The 2-KGA was determined by thin-layer chromatography, Lanning and Cohen’s method, and high-performance liquid chromatography. After fermentation in a minimal liquid medium for 24 hours, the bacterium showcased its prowess by producing 2-KGA concentrations of 7.5 g/L. However, the purity of the 2-KGA production is paramount for industrial applications. In addressing this, a rigorous chromatographic purification regimen was employed. This involved two sequential stages of ion exchange chromatography, DEAE-Sephacel and DOWEX 1X4, followed by Superdex^TM S-200 column chromatography. The collective efficacy of these methodologies yielded a product with an impressive purity index of 71.02%. The 2-KGA product was then subjected to a decolorization process using activated carbon and freeze-dried. This results in the compound being a pure white powder. This investigation indicates that N. vanlangensis KKS-R1 shows good potential as a 2-KGA producer at high temperatures. Under proper purification techniques. These findings contribute to developing purified processes and producing 2-KGA for industrial efficiency.