The overall aim of this investigation was to identify novel bacterial and fungal biocatalytic routes towards monoterpene alcohols such as enantiopure linalool and menthol, and geraniol, each of which find many applications within the flavour and fragrance industries. The first part of the investigation targeted hydrolytic transformations of racemic monoterpene esters. Enantioselective linalyl acetate esterase activity was detected in Rhodococcus ruber DSM 43338, offering a potential route towards enantiopure (R)- and (S)- linalool. Fractions displaying complementary enantioselectivity for the reaction were isolated from anion-exchange chromatography of cell extracts, giving enantiomeric excess values for linalool ranging from 60% (R)- to 79% (S)-. Attempts to isolate the genes encoding relevant esterases via polymerase chain reactions resulted in a gene fragment representing 75% of a putative tertiary alcohol esterase (TAE). An alternative gene putatively encoding a TAB from a closely related Actinomycete Nocardia farcinica (NITAE) was cloned and expressed in E. coli, and the enzyme purified and characterised. NITAE was inactive towards linalyl acetate, but catalysed the hydrolysis of racemic menthyl acetate to give the commercially-preferred 1(R)-enantiomer of menthol. In the second part of the project, a strain of Rhodococcus erythropolis MLTl was isolated by selective enrichment from soil surrounding hop plants using the hop terpene f3-myrcene as sole carbon source. Resting-cell preparations transformed 13- myrcene to the high-value monoterpene alcohol geraniol. While the relevant enzyme remains to be identified, initial studies suggested an inducible operon for f3-myrcene degradation in MLTl.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:516657 |
| Date | January 2009 |
| Creators | Thompson, Mark Lawrence |
| Publisher | University of York |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://etheses.whiterose.ac.uk/14210/ |
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