| Summary: | <p>The aim of this thesis was to improve the understanding of how bacteria (in
particular Rhodococcus rhodochrous LL100-21) use enzymatic reactions to
biotransform nitrile compounds. Particular emphasis was given to some compounds
of potential interest to the pharmaceutical industry.</p>
<p>Due to the difficulty in selectively converting one cyano group of a polynitrile
by conventional chemical techniques, regioselectivity of Rhodococcus rhodochrous
LL100-21 was investigated using (cyanomethyl) benzonitrile compounds. Depending
on the induction/growth conditions and the position of ring substitution of the
substrate, different products were obtained following the biotransformation. For
example, bacteria grown/induced on propionitrile or benzonitrile converted the
substrate 2-(cyanomethyl) benzonitrile to 2-(cyanophenyl) acetic acid- with a 64 %
yield compared to the starting substrate. Conversely, bacteria grown on acetonitrile
converted the same substrate to a mixture of amide intermediates but at very low
yield. Furthermore, the aliphatic cyano group of 2-(cyanomethyl) benzonitrile was
preferentially hydrolysed. In the case of 3- and 4-(cyanomethyl) benzonitrile, the
aromatic cyano group was converted to the acid thereby suggesting ring substitution
was an important factor in the biotransformation.</p>
<p>Initial rate studies were undertaken in order to greater understand the
biotransformations. The results suggested that steric hindrance influenced the
reaction. Furthermore, when there was a cyano or bromo group in the ortho position
of the aromatic ring it was found that there was an in increase in the initial rate of
hydrolysis, suggesting these groups also affect the enzymatic reaction.</p>
<p>In addition, PCR and Southern blot techniques were used to investigate the presence
of nitrile hydrolysing enzymes in a range of bacteria.</p>
<p>Mid infrared spectroscopy was carried out to study the enzyme kinetics
involved in nitrile biotransformations permitting, for the first time, nitrile
biotransformations to be monitored in real-time. This opens up React IR MP as a
useful technique for studying a wide range of biocatalytic processes in real-time.
Bioconversion of prochiral nitriles was also undertaken using Rhodococcus
rhodochrous LL100-21. The results suggested that the bacterium could biotransform
these nitriles and, with further chemical rearrangement, could yield novel compounds
of interest to the pharmaceutical industry.</p>
<p>Finally, the biotransformation of benzonitrile was undertaken in the presence
of hydroxylamine (NH2OH), which is more nucleophilic than water. Interestingly,
when bacteria were grown on benzonitrile (to induce the nitrilase enzyme) the
hydroxylamine competed with the water and the novel product, benzohydroxamic
acid, was foiuied. Furthermore, the abiotic control afforded another product
benzamide oxime.</p>
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