title: Equilibrium modeling of extractive enzymatic hydrolysis of penicillin G with concomitant 6-aminopenicillanic acid crystallization.
abstract: In the present downstream processing of penicillin G, penicillin G is extracted from the fermentation broth with an organic solvent and purified as a potassium salt via a number of back-extraction and crystallization steps. After purification, penicillin G is hydrolyzed to 6-aminopenicillanic acid, a precursor for many semisynthetic beta-lactam antibiotics. We are studying a reduction in the number of pH shifts involved and hence a large reduction in the waste salt production. To this end, the organic penicillin G extract is directly to be added to an aqueous immobilized enzyme suspension reactor and hydrolyzed by extractive catalysis. We found that this conversion can exceed 90% because crystallization of 6-aminopenicillanic acid shifts the equilibrium to the product side. A model was developed for predicting the equilibrium conversion in batch systems containing both a water and a butyl acetate phase, with either potassium or D-p-hydroxyphenylglycine methyl ester as counter-ion of penicillin G. The model incorporates the partitioning equilibrium of the reactants, the enzymatic reaction equilibrium, and the crystallization equilibrium of 6-aminopenicillanic acid. The model predicted the equilibrium conversion of Pen G quite reasonably for different values of pH, initial penicillin G concentration and phase volume ratio. The model can be used as a tool for optimizing the enzymatic hydrolysis.
authors.affiliation: Delft University of Technology, Kluyver Laboratory for Biotechnology, Julianalaan 67, NL-2628 BC Delft, The Netherlands.
authors.forename: M B
authors.initials: MB
authors.lastname: Diender
authors.forename: A J J
authors.initials: AJ
authors.lastname: Straathof
authors.forename: T
authors.initials: T
authors.lastname: van der Does
authors.forename: C
authors.initials: C
authors.lastname: Ras
authors.forename: J J
authors.initials: JJ
authors.lastname: Heijnen
mesh_terms: D000085:Acetates / Q000378:metabolism*; D002384:Catalysis; D002851:Chromatography, High Pressure Liquid / Q000379:methods; D003198:Computer Simulation; D003460:Crystallization; D004926:Escherichia coli / Q000201:enzymology; D005285:Fermentation; D005998:Glycine / Q000031:analogs & derivatives* / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D006868:Hydrolysis; D008956:Models, Chemical; D010397:Penicillanic Acid / Q000031:analogs & derivatives / Q000737:chemistry / Q000302:isolation & purification* / Q000378:metabolism*; D010399:Penicillin Amidase / Q000378:metabolism; D010400:Penicillin G / Q000302:isolation & purification / Q000378:metabolism*; D011188:Potassium / Q000737:chemistry; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014867:Water / Q000737:chemistry
chemical_list: D000085:Acetates; D014867:Water; C006848:butyl acetate; C023010:4-hydroxyphenylglycine; D010397:Penicillanic Acid; D010399:Penicillin Amidase; D010400:Penicillin G; C004408:aminopenicillanic acid; D011188:Potassium; D005998:Glycine