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Appl Biochem Biotechnol (2013) 170:14821490
DOI 10.1007/s12010-013-0282-3
Received: 17 January 2013 /Accepted: 2 May 2013 /
Published online: 19 May 2013# Springer Science+Business Media New York 2013
Abstract The synthesis of the aroma chemical cinnamyl alcohol (CMO) by means of enzymatic reduction of cinnamaldehyde (CMA) was investigated using NADH-dependent alcohol dehydrogenase from Bacillus stearothermophilus both as an isolated enzyme, and in recombinant Escherichia coli whole cells. The influence of parameters such as reaction time and cofactor, substrate, co-substrate 2-propanol and biocatalyst concentrations on the bioreduction reaction was investigated and an efficient and sustainable one-phase system developed. The reduction of CMA (0.5 g/L, 3.8 mmol/L) by the isolated enzyme occurred in 3 h at 50 C with 97 % conversion, and yielded high purity CMO (98 %) with a yield of 88 %
and a productivity of 50 g/genzyme. The reduction of 12.5 g/L (94 mmol/L) CMA by whole cells in 6 h, at 37 C and no requirement of external cofactor occurred with 97 % conversion, 82 %
yield of 98 % pure alcohol and a productivity of 34 mg/gwet cell weight. The results demonstrate
the microbial system as a practical and efficient method for larger-scale synthesis of CMO.
Keywords Cinnamyl alcohol . Aroma chemicals . Alcohol dehydrogenase . Cofactor recycling . Bacillus stearothermophilus
Introduction
Cinnamyl alcohol (CMO) is a versatile chemical due to its aroma and its fixative properties; it is used in the fragrance and flavouring industries for cinnamon notes and the rounding off of fruit aromas. It is also a valuable intermediate for the production of aroma-relevant esters [1], the syntheses of the Taxols C13 side chain [2], the antibiotic Chloromycetin [3] and the antidepressant reboxetine mesylate [4]. CMO can be prepared by chemical reduction of cinnamaldehyde (CMA) under different heterogeneous catalysis conditions [5, 6]. However, selective hydrogenation of CO over CC is still an important issue since, besides the desired unsaturated alcohol, the process can lead to non-desirable saturated aldehyde and alcohol as side-products that may result in odour performance issues. Moreover, the use of
A. Pennacchio : M. Rossi : C. A. Raia (*)
Istituto di Biochimica delle Proteine, CNR, Via P. Castellino 111, 80131 Naples, Italy e-mail: [email protected]
Synthesis of Cinnamyl Alcohol from Cinnamaldehyde with Bacillus stearothermophilus Alcohol Dehydrogenase...