Lynch, Raymond Michael; (1995) Process design for the oxidation of fluorobenzene to fluorocatechol using Pseudomonas putida ML2. Doctoral thesis (Ph.D), UCL (University College London).

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Abstract

In this thesis, a framework for biotransformation process design has been outlined. A particular biotransformation (the microbial oxidation of fluorobenzene to fluorocatechol) was chosen to illustrate the benefits of adopting such a structured approach. This reaction system is characterized by the following: Fluorobenzene (the poorly aqueous soluble, volatile substrate) causes reversible, cellular activity inhibition at 0.8g/L. First order kinetics are observed for fluorobenzene conversion up to 0.1g/L, after which, zero order kinetics apply. Fluorocatechol (the completely aqueous soluble product) is toxic at 0.2g/L causing irreversible activity loss. An assay capable of measuring the intrinsic biocatalytic activity of the cells has been developed. These characterization data have been used to define a number of process options. One of these has been developed to promote production levels up to seventy times the cellular toxicity limit of the biocatalyst (0.185g fluorocatechol/g dry wt/hr) for 11 hours operation. Ten modes of oxygen supply were evaluated including a novel membrane oxygenator, a perfluorocarbon, a solvent, head pressurisation and oxygen enrichment. Two modes (membrane oxygenator and pure oxygen) were analysed during continuous biotransformations for their ability to eliminate fluorobenzene volatilization loss. The membrane oxygenator completely eliminated all fluorobenzene loss from the biotransformation. 13 conclusions have been drawn which are listed on page 120. By adopting the biotransformation process design framework presented in this thesis, a bioreactor configuration has been developed which has successfully overcome the difficulties associated with oxygen supply to a whole cell catalysed, aromatic oxidation having a volatile, inhibitory, poorly aqueous soluble substrate and a toxic, completely aqueous soluble product.

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