Kinetic study for the extraction of succinic acid with TOA in fermentation broth; effects of pH, salt and contaminated acid

https://doi.org/10.1016/j.bej.2006.06.011Get rights and content

Abstract

Reactive extraction can be used for the recovery of carboxylic acids from fermentation broth. Through the formation of complex with extractants at the two-phase interface, the carboxylic acids are partitioned into organic solvents. However, the recovery of carboxylic acids is interrupted by the conditions of fermentation broth. In this study, the effects of conditions of fermentation broth on the extraction kinetics were investigated using a microporous membrane-based stirred cell for the extraction of succinic acid with tri-n-octylamine. The interfacial concentrations of species in various systems were correlated and thus the effects of pH, salts and contaminated acid on the intrinsic reaction kinetics were discovered. The reaction rate constants were determined from the forward reaction rate equation reported in our previous work. It was found that the extraction rates were steeply decreased at pH values larger than 3 due to the dissociation of carboxylic group. Competitive extraction of salts, which were HPO42− (or PO43−), CO32− and SO42−, and contaminated acid, which was pyruvic acid, had negative influence on the extraction process of succinic acid and thus the extraction rates were decreased. The interfacial concentrations of succinic acid and TOA in fermentation broth had no difference with those in artificial single acid systems. Therefore, the decrease of extraction rates can be explained by the change of ionic strength in fermentation broth.

Introduction

Succinic acid is a dicarboxylic acid which has attracted great interest as a green feed stock for the manufacture of synthetic resins, biodegradable polymers and chemical intermediates [1]. It can be produced as an intermediate of tricarboxylic acid cycle (TCA) and also as one of the fermentation products of anaerobic metabolism [2]. Actinobacillus succinogenes and Mannheimia succiniciproducens, which were discovered as facultative anaerobic bacteria, are newly considered as effective succinic acid producers due to the high productivity of succinic acid [3], [4].

Production process of succinic acid by fermentation consists of product recovery, concentration, acidification and purification. Since the required purity cannot be acquired by only one process, several techniques, such as electrodialysis, crystallization, distillation and extraction, are employed for its production [5], [6], [7], [8]. The traditional product recovery is based on successive processes of acidification, crystallization and acidification by ion-exchange resins [9], [10]. Recently, reactive extraction, which makes a complex with the functional group of a solute, has been shown to be a promising technique for the recovery of carboxylic acids from aqueous solutions [11], [12], [13].

In the production process of succinic acid by fermentation, contaminated organic acids such as acetic and pyruvic acids are also produced simultaneously. In addition, there are some impurities, such as carbon sources and salts, in fermentation broth [3], [4]. If the extraction process of succinic acid in fermentation broth should be established on a large scale, kinetic and equilibrium studies about the effects of impurities and contaminated acids on the extraction should be conducted. Although a small number of equilibrium studies referred to the adverse effect of impurities and contaminated acids on the recovery of carboxylic acids, there are few works on the extraction kinetics [14], [15], [16], [17].

In this work, the effects of impurities and contaminated acids on the extraction kinetics of succinic acids were investigated. The interfacial concentrations were correlated and the intrinsic forward reaction rate equation, which was reported in our previous work [18], was used to determine the reaction rate constants. The effects of pH, contaminated acids and salts on the extraction rates and rate constants were investigated in various systems.

Section snippets

Microorganism and growth

M. succiniciproducens was grown in the same way reported in Ref. [3].

Artificial aqueous solutions of succinic acid

In a single acid system, succinic acid (Sigma, 99%) was dissolved in distilled water. The initial concentration of succinic acid was 188.84 mol m−3. This concentration was based on the concentration of practical fermentation broth produced by M. succiniciproducens.

In a binary acid system, succinic and pyruvic acids (Sigma, 99%) were dissolved in distilled water together. The initial concentration of succinic acid was 188.84 mol m−3

Determination of mass-transfer coefficients

The individual mass-transfer coefficients of iodine in the bulk aqueous phase, the bulk organic phase and the membrane phase could be determined from the diffusion experiments of iodine in water/kerosene and water/n-heptane systems [18]. Based on Eqs. (1) and (2) [20], the mass-transfer coefficients of succinic acid in the aqueous phase and TOA in the organic phases were correlated [18].ka,koDj2/3γ1/6km=Djεδmτ

The diffusivities of iodine, succinic acid and TOA are estimated by Minhas-Hayduk

Conclusions

The effects of pH, salts and contaminated acids on the extraction kinetics were investigated using microporous membrane-based stirred cell.

The reaction rates were affected by pH due to the dissociation of succinic acid in the aqueous phase. The presence of contaminated acid and salts had adverse effects on the extraction process of succinic acid because of the co-extraction by amine extractants. The reaction rate constants were also affected by pH and the presence of salts and contaminated acid

Acknowledgements

This work was supported by the Genome-based Integrated Bioprocess Project of the Ministry of Science and Technology and the Brain Korea 21 (BK21).

References (29)

  • J.A. Tamada et al.

    Extraction of carboxylic acids with amine extractions. 1. Equilibria and law of mass action modeling

    Ind. Eng. Chem. Res.

    (1990)
  • R. Datta, Process for the production of succinic acid by anaerobic fermentation, US patent 5,143,833...
  • K.A. Berglund, P. Elankovan, D.A. Glassner, Carboxylic acid purification and crystallization process, US patent...
  • Y.K. Hong et al.

    Extraction of succinic acid with 1-octanol/n-heptane of mixed tertiary amine

    Bioprocess. Eng.

    (2000)
  • Cited by (0)

    View full text