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Asymmetric reduction of α, β‐unsaturated ketone to ( R ) allylic alcohol by Candida chilensis
Author(s) -
Pollard D.J.,
Telari K.,
Lane J.,
Humphrey G.,
McWilliams C.,
Nidositko S.,
Salmon P.,
Moore J.
Publication year - 2006
Publication title -
biotechnology and bioengineering
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.136
H-Index - 189
eISSN - 1097-0290
pISSN - 0006-3592
DOI - 10.1002/bit.20751
Subject(s) - ketone , allylic alcohol , alcohol , allylic rearrangement , chemistry , reduction (mathematics) , stereochemistry , organic chemistry , catalysis , mathematics , geometry
Abstract A pilot scale whole cell process was developed for the enantioselective 1,2‐reduction of prochiral α,β‐unsaturated ketone to ( R ) allylic alcohol using Candida chilensis . Initial development showed high enantiomeric excess (EE > 95%) but low product yield (10%). Process development, using a combination of statistically designed screening and optimization experiments, improved the desired alcohol yield to 90%. The fermentation growth stage, particularly medium composition and growth pH, had a significant impact on the bioconversion while process characterization identified diverse challenges including the presence of multiple enzymes, substrate/product toxicity, and biphasic cellular morphology. Manipulating the fermentation media allowed control of the whole cell morphology to a predominately unicellular broth, away from the viscous pseudohyphae, which were detrimental to the bioconversion. The activity of a competing enzyme, which produced the undesired saturated ketone and ( R ) saturated alcohol, was minimized to ≤5% by controlling the reaction pH, temperature, substrate concentration, and biomass level. Despite the toxicity effects limiting the volumetric productivity, a reproducible and scaleable process was demonstrated at pilot scale with high enantioselectivity (EE > 95%) and overall yield greater than 80%. This was the preferred route compared to a partially purified process using ultra centrifugation, which led to improved volumetric productivity but reduced yield (g/day). The whole cell approach proved to be a valuable alternative to chemical reduction routes, as an intermediate step for the asymmetric synthesis of an integrin receptor anatagonist for the inhibition of bone resorption and treatment of osteoporosis. © 2006 Wiley Periodicals, Inc.