(117a) Continuous Manufacturing of Beta-Lactam Antibiotics By Enzymatic Synthesis and Crystallization: A Pilot Plant Study

Authors: 
Salami, H. - Presenter, Georgia Institute of Technology
Harris, P., Georgia Institute of Technology
Lagerman, C., Georgia Institute of Technology
McDonald, M., Georgia Tech
Rousseau, R., Georgia Institute of Technology
Grover, M., Georgia Tech
Bommarius, A., Georgia Institute of Technology
Semi-synthetic antibiotics such as ampicillin, amoxicillin, and cephalexin are commonly used to treat certain bacterial infections. Advances in biocatalyst development led to a paradigm shift in the industry where the simpler enzymatic synthesis replaced the complex and wasteful chemical route, leading to significantly less solvent and energy consumption in the production process and improving the process green chemistry metrics [1]. We have recently reported that by combining the enzymatic synthesis with a crystallization the yield and selectivity of this process can be improved by suppressing the product hydrolysis by the biocatalyst (Fig. 1a) [2]. Besides the synergy between reaction and crystallization, another way to improve this process efficiency and environmental impact is by exploiting the benefits of continuous manufacturing, such as the ability to process higher concentrations of reactants, relatively smaller size, shorter downtime, and higher flexibility in process operation and control [1,3]. Operating this process continuously can enhance process attributes such as productivity and space-time yield, which manifests itself, again, in improved green chemistry scores such as lower E-factor.

In this contribution, we first review our efforts on building a mathematical model for this process and extensive simulations (1) to guide the process development for the construction of a pilot plant producing > 1 g/h of amoxicillin trihydrate and cephalexin monohydrate crystals, and (2) to identify the optimum process operating point (Fig. 1b) [2,4-5]. Our analysis points to a delicate trade-off between several process parameters such as pH, enzyme concentration, and residence time leading to a non-trivial optimization problem with several constraints dictated by critical quality attributes of the final product such as solid-phase purity. We have successfully illustrated the continuous production of cephalexin monohydrate at > 99% purity, with a productivity of 1-4 g/h for over 20 h of continuous operation. Putting a strong emphasis on the quality attributes of the product, we will briefly discuss the development of our process from the quality by design viewpoint, and will present the results of our risk assessment studies to identify the critical process parameters.

Fig.1. Main reactions in the enzymatic synthesis using Pen. G Acylase (PGA); enzyme catalyzes the synthesis of the API from an activated acyl donor (e.g., PGME) and a nucleophile containing the beta-lactam core (e.g., 7-ADCA), in addition to hydrolysis of the acyl donor and the API (a). Process simulations for identification of optimum operating point for cephalexin production (b). Example of data acquired during pilot plant operation (c). Example of online and offline product characterization (d).

Cited literature

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[2] McDonald, Matthew A., Andreas S. Bommarius, and Ronald W. Rousseau. "Enzymatic reactive crystallization for improving ampicillin synthesis." Chemical Engineering Science 165 (2017): 81-88.

[3] Acevedo, David, Xiaochuan Yang, Adil Mohammad, Naresh Pavurala, Wei-Lee Wu, Thomas F. O’Connor, Zoltan K. Nagy, and Celia N. Cruz. "Raman spectroscopy for monitoring the continuous crystallization of carbamazepine." Organic Process Research & Development 22, no. 2 (2018): 156-165.

[4] Salami, Hossein, Colton E. Lagerman, Patrick R. Harris, Matthew A. McDonald, Andreas S. Bommarius, Ronald W. Rousseau, and Martha A. Grover. "Model development for enzymatic reactive crystallization of β-lactam antibiotics: a reaction–diffusion-crystallization approach." Reaction Chemistry & Engineering 5, no. 11 (2020): 2064-2080.

[5] McDonald, Matthew A., Andreas S. Bommarius, Ronald W. Rousseau, and Martha A. Grover. "Continuous reactive crystallization of β-lactam antibiotics catalyzed by penicillin G acylase. Part I: Model development." Computers & Chemical Engineering 123 (2019): 331-343.