As an important  C₄ platform chemical, succinic acid is widely used as the precursor of numerous products, such as pharmaceuticals, food additives, green solvents, and biodegradable polymers. As we well known, some by-products, such as formic acid, ethanol, acetic acid, are usually yielded in the process of microbial fermentation of succinic acid production. These by-products could influence the quality of succinic acid. Hence, it is important to determine these components in a fermentation broth. As reported in literatures, various chromatographic methods had been used to analyze the components of succinic acid fermentation broth, but with many disadvantages. Therefore, it is significant for the development of the analytic method for succinic acid fermentation broth.

The researchers from Qingdao Institute of Bioenergy and Bioprocess Technology (QIBEBT) of the Chinese Academy Sciences firstly introduced diffusion-ordered NMR spectroscopy (DOSY) protocol to directly analyze the mixture samples of succinic acid fermentation broth.

The results indicated that DOSY technique could be effectively used to directly determine the composition of a model mixture (sample 1) of L-tartaric acid, L-malic acid, fumaric acid, maleic acid, citric acid, and succinic acid (Figure 1 left). Interestingly, the compounds with same or similar molecular weights were clearly distinguished in the DOSY spectra according to their different solvation. However, these compounds could not be separated baseline by ionic chromatography (IC) technique (Figure 1 right). The peaks of some isomers were even completely overlapping in the IC chromatogram. The excellent qualitative analysis result demonstrated that DOSY technique can play a great role in the determination of the product quality of succinic acid fermentation broth.

This study was recently published on ACS Sustainable Chemistry & Engineering. This research was supported by the National Natural Science Foundation of China and was led by Dr. Shaohua Huang from Public Laboratory, QIBEBT, CAS.

Figure 1. (left) 2D  1H DOSY spectrum recorded at 600 MHz in D2O of sample 1 at 298 K. (right) IC separation of sample 1 on the ICS-5000 with conductivity detection. Peaks: 1, L-malic acid; 2, succinic acid; 3, L-tartaric acid; 4, fumaric acid; 5, maleic acid; 6, citric acid. Chromatographic conditions: mobile phase: 30 mM KOH aqueous solution; flow rate: 1.0 mL min-1; column temperature: 303 K.

Reference:

1.     Wang, L. M.; Yang, Y.; Yang, H. Y.; Qiu, R. C.*; Huang, S. H.* Direct analysis of succinic acid fermentation broth by ¹H diffusion-ordered NMR spectroscopy and quantitative ¹H NMR technique. ACS Sustainable Chem. Eng. 2017, 5：2824-2828.  

Contact:

Dr. Shaohua Huang

Email: huangsh(AT)qibebt.ac.cn

Web: http://english.qibebt.cas.cn