Screening among constructive and operating alternatives when designing an enzymatic reactor [articol]

Abstract

Optimal design and operation of enzymatic processes is a fundamental engineering problem to be solved when laboratory-scale kinetic data and enzyme characteristics are available. The final decision is based on a comparative analysis of reactor performances by accounting for various optimal/sub-optimal operating alternatives, enzyme activity and stability, materials and operation costs, purification steps, and product value. Due to the high complexity of the engineering problem, development of a library of quickly adaptable reactor models allows evaluation of process scaling-up alternatives, in terms of reactor type (well-mixed vs. plug-flow), enzyme use (free-enzyme vs. immobilized enzyme), or operation mode (simple batch, batch with intermittent addition of enzyme following certain optimal policies, semi-batch with uniform or optimal enzyme feeding policy, fixed-bed or fluidized-bed continuous reactors with time-optimal feeding policies). Analysis of process dynamics under various operating conditions for fast, moderate fast, or slow deactivating enzyme leads to choose the most suitable reactor and operation mode based on several performance indices (enzyme specific consumption and stability, reactor productivity, operating time, easy operability and control, etc.). Two case studies exemplify this comparative analysis, that is the design of an industrial reactor for D-glucose enzymatic oxidation (using free pyranose oxidase), and the design of an industrial reactor for inulin enzymatic hydrolysis (using free or immobilized inulinase). Model-based simulations of the enzymatic reactors suggest optimal operation policies according to the enzymes variable characteristics.