CHOICE OF MICROBIAL HOST FOR THE NAPHTHALENE DIOXYGENASE BIOCONVERSION

The use of whole cell biotransformations for single and multistep enzy me conversions is gaining widespread application. In this study the na phthalene dioxygenase nah A gene was transferred into Pseudomonas aeru ginosa PAC 1R, Escherichia coli JM107 and Pseudomonas putida PpG 277, The effect of ethanol on these genetically engineered Gram-negative ba cteria was studied by measurement of enzyme activity, stability and ce ll integrity, Ethanol has been used in biotransformations as a co-subs trate carbon source for co-factor recycling and as a co-solvent increa sing dissolved substrate and product levels. Ethanol increased the dis solved substrate (naphthalene) concentration slightly and dissolved pr oduct ((+)-cis-(1R,2S)-dihydroxy-1,2-dihydronaphthalene) by approximat ely 30% at 4% (w/v) ethanol, Both P. aeruginosa PAC 1R and P. putida P pG 277 showed decreased activity with increasing ethanol concentration whilst E. coli enzyme activity increased with increasing ethanol conc entration being comparable to that when glucose was used as a carbon s ource. This project highlighted the many factors involved in the selec tion of microbial hosts for whole cell biotransformation processes.