The toxicity of aromatics frequently limits the yields of their microbial synthesis. For example, the 5% yield of
catechol synthesized from
glucose by Escherichia coli WN1/pWL1.290A under
fermentor-controlled conditions reflects
catechol's microbial toxicity. Use of in situ resin-based extraction to reduce
catechol's concentration in culture medium and thereby its microbial toxicity during its synthesis from
glucose by E. coli WN1/pWL1.290A led to
a 7% yield of
catechol. Interfacing microbial with chemical synthesis was then explored where
glucose was microbially converted into a nontoxic intermediate followed by chemical conversion of this intermediate into
catechol. Intermediates examined include
3-dehydroquinate,
3-dehydroshikimate, and protocatechuate.
3-Dehydroquinate and
3-dehydroshikimate synthesized, respectively, by E. coli QP1.1/pJY1.216A and E. coli KL3/pJY1.216A from
glucose were extracted and then reacted in water heated at 290 degrees C to afford
catechol in overall yields from
glucose of 10% and 26%, respectively. The problematic extraction of these
catechol precursors from culture medium was subsequently circumvented by high-yielding chemical
dehydration of
3-dehydroquinate and
3-dehydroshikimate in culture medium followed by extraction of the resulting protocatechuate. After reaction of protocatechuate in water heated at 290 degrees C, the overall yields of
catechol synthesized from
glucose via chemical
dehydration of
3-dehydroquinate and chemical
dehydration of
3-dehydroshikimate were, respectively, 25% and 30%. Direct synthesis of protocatechuate from
glucose using E. coli KL3/pWL2.46B followed by its extraction and chemical decarboxylation in water gave a 24% overall yield of
catechol from
glucose. In situ resin-based extraction of protocatechaute synthesized by E. coli KL3/pWL2.46B followed by chemical decarboxylation of this
catechol percursor was then examined. This employment of both strategies for dealing with the microbial toxicity of aromatic products led to the highest overall yield with
catechol synthesized in 43% overall yield from
glucose.