title: Biphasic aqueous/organic biotransformation of acetaldehyde and benzaldehyde by Zymomonas mobilis pyruvate decarboxylase.
abstract: Zymomonas mobilis pyruvate decarboxylase (PDC) transformed acetaldehyde and benzaldehyde into (R)-phenylacetylcarbinol (PAC), the precursor for the synthesis of ephedrine and pseudoephedrine. Organic solvents were screened for a biphasic biotransformation with the enzyme in an aqueous phase and the toxic substrates delivered through the organic phase. In the absence of substrates a second phase of 1-pentanol, hexadecane or MTBE (methyl tertiary-butyl ether) stabilized the PDC activity in comparison to a control without added solvent. Organic phase solvents for optimal PAC production had partitioning coefficient (log P) values between 0.8 and 2.8 (production of more than 8 mg PAC/ U PDC), however there was no correlation between enzyme stability and log P. Best PAC formation was observed with the eight tested alcohols, which in contrast to the other solvents allowed lower initial concentrations of toxic acetaldehyde (54-81 mM) in the aqueous phase. 1-pentanol, 1-hexanol, and isobutanol resulted in the highest specific PAC production of 11 mg PAC /U PDC. Without the addition of an organic phase, only 1.2 mg/U was formed.
authors.affiliation: School of Biotechnology and Biomolecular Sciences, University of New South Wales, Sydney NSW 2052, Australia. b.rosche@unsw.edu.au
authors.forename: Bettina
authors.initials: B
authors.lastname: Rosche
authors.forename: Michael
authors.initials: M
authors.lastname: Breuer
authors.forename: Bernhard
authors.initials: B
authors.lastname: Hauer
authors.forename: Peter L
authors.initials: PL
authors.lastname: Rogers
mesh_terms: D000079:Acetaldehyde / Q000032:analysis / Q000737:chemistry / Q000378:metabolism*; D000096:Acetone / Q000031:analogs & derivatives* / Q000032:analysis / Q000737:chemistry; D001547:Benzaldehydes / Q000032:analysis / Q000737:chemistry / Q000378:metabolism*; D001711:Biotransformation; D011767:Pyruvate Decarboxylase / Q000737:chemistry / Q000378:metabolism*; D012997:Solvents / Q000737:chemistry; D017355:Zymomonas / Q000201:enzymology*
chemical_list: D001547:Benzaldehydes; D012997:Solvents; D000096:Acetone; C035293:1-hydroxy-1-phenyl-2-propanone; D011767:Pyruvate Decarboxylase; D000079:Acetaldehyde; C032175:benzaldehyde