Modelling of immobilised enzyme biocatalytic membrane reactor performance

• An immobilised enzyme biocatalytic membrane reactor (BMR) was developed and modelled.
• Amidase-catalysed lactamide to lactic acid was used as an industrially representative system.
• The model was empirically validated using different amide and amidase concentrations and feed rates.
• The model predicted critical parameter ranges defining maximum conversion in the BMR process.
• The model is applicable to enzyme-catalysed BMRs, irrespective of the enzyme or substrate moieties.

Immobilised enzyme-catalysed conversions frequently provide specific advantages of selectivity over chemical conversions and further, facilitate continuous operation through biocatalyst retention and reuse. This study focuses on the development and modelling of an enzyme-catalysed continuous immobilised enzyme biocatalytic membrane reactor (BMR). The conversion of the amidase-catalysed lactamide to lactic acid process was used as an industrially representative system with which to evaluate the process performance of the BMR.The model was developed from unsteady state differential mass balances incorporating a second order enzyme decay. This model was validated from empirically determined conversions in dual experiments using 80 and 40 mM amide substrate, 6.4 and 20.1 mg immobilised amidase and a flow rate of 0.0005 and 0.0001 L/min respectively.Model predictions over a range of amidase amounts and stabilities, flow rates and initial amide concentrations quantified the direction and extent of the influence of these parameters on the maximum conversions attainable, consequently identifying the critical parameter ranges defining optimal BMR performance. Although the model has been developed and validated for the prediction of BMR performance of the specific lactamide-lactic acid system, it nevertheless has broad applicability for and relevance to broad-based prediction of the performance of immobilised enzyme BMR processes in general, irrespective of the specific enzyme or substrate moieties.

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