Discrete Countercurrent Contacting:  An Experimental Method for Developing Continuous Countercurrent Reactors

Abstract

To facilitate experimental studies on countercurrent reactors, a discrete contacting mode was worked out experimentally and theoretically. Enzymatic hydrolysis of penicillin G to phenylacetic acid and 6-aminopenicillanic acid was carried out in biphasic aqueous organic systems without pH control. The two phases were countercurrently contacted in a discrete manner, so that equilibrium was reached in each stage. Sets of three and five shake flasks served to mimic equilibrium stages in the countercurrent setup. It was shown that discrete countercurrent contact leads to the same extent of improvement of the equilibrium conversion as continuous countercurrent contact does, when compared to the batch situation. Therefore, discrete experiments may be used to simplify the development of continuous countercurrent reactors.

Reactive Separations for In Situ Product Removal of Enzymatic Reactions: A Review

“…The group around van der Wielen and Straathof [119,174,[181][182][183]] applied a biphasic system containing water/ butyl acetate for the penicillin G hydrolysis to perform a reactive separation of phenylacetic acid and 6-aminopenicillanic acid to minimize the downstream process. Moreover, den Hollander et al [174] described a countercurrent mixer-settler for the application of a quasi-continuous process.…”

An Eco-Friendly and Sustainable Process for Enzymatic Hydrolysis of Penicillin G in Cloud Point System

“…The coacervate phase was withdrawn in every 2 h of hydrolysis process, and it was back extracted with equivalent volume of water at pH above 7. The coacervate phase of back-extraction was reused in the next run of enzymatic hydrolysis process again operation [3]. The result of a discrete semi-batch process was shown in Fig.…”

“…As replacement of the coacervate phase to the 4th time, the enzymatic hydrolysis of Pen G reached a nearly complete conversion. Compared to extractive enzymatic hydrolysis in aqueous-organic solvent biphasic system without pH control in a discrete continuous countercurrent operation mode (where the APA concentration in aqueous phase was about 25 mM in the third run [2] and about 70 mM in the fifth run [3]), the accumulated product concentration in the diluted phase of cloud point system had been improved markedly. Discrete semi-batch process envisages that a high conversion yield can be obtained by semi-continuous process mode with a continuous flow of the coacervate phase.…”

“…The Pen G crystal is used for production of APA by enzymatic hydrolysis at a controlled pH 7-8. This process is not sustainable since it consumes an alkali (ammonia), an acid (sulfuric acid) and generates a large amount of wastes including ammonium sulfate [2,3].…”

“…Extractive biocatalysis, i.e., coupling of a bioreaction unit with a product extraction unit in a biphasic system, has been described for enzymatic hydrolysis of Pen G by many researchers [2][3][4][5][6][7]. The extraction of phenylacetic acid (PAA) to a non-biocatalysis reaction phase makes the enzymatic hydrolysis without pH control possible [2,3], even direct hydrolysis of the Pen G from its fermentation broth [4]. However, the PAA extraction ability of aqueous-organic solvent biphasic systems is limited at a relatively high pH [4].…”