Abstract
Pilot-scale reactive-extraction technology for fully integrated
L-phenylalanine (L-Phe) separation in Escherichia coli fed-batch
fermentations was investigated in order to prevent an inhibition of
microbial L-Phe production by-product accumulation. An optimal
reactive-extraction system, consisting of an organic kerosene phase with
the cation-selective carrier DEHPA (di-2-ethylhexyl phosphonic acid) and
an aqueous stripping phase including sulphuric acid, was found
particularly efficient. Using this system with two membrane contactors,
mass-transfer coefficients of up to 288x10(-7) cm s(-1) for the
aqueous/organic and 77x10(-7) cm s(-1) for the organic/stripping phase
were derived from experimental data using a simple modelling approach.
Concentration factors higher than 4 were achieved in the stripping phase
as compared to the aqueous donor phase. Reactive extraction enabled a
98\% cation portion of L-Phe in the stripping phase, leading to final
product purity higher than 99\% after L-Phe precipitation. A doubling of
L-Phe/glucose yield was observed when kerosene/DEHPA was added to the
fermentation solution in the bioreactor to experimentally simulate a
fully integrated L-Phe separation process.
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