title: Optimization of enzymatic gas-phase reactions by increasing the long-term stability of the catalyst.
abstract: Enzymatic gas-phase reactions are usually performed in continuous reactors, and thus very stable and active catalysts are required to perform such transformations on cost-effective levels. The present work is concerned with the reduction of gaseous acetophenone to enantiomerically pure (R)-1-phenylethanol catalyzed by solid alcohol dehydrogenase from Lactobacillus brevis (LBADH), immobilized onto glass beads. Initially, the catalyst preparation displayed a half-life of 1 day under reaction conditions at 40 degrees C and at a water activity of 0.5. It was shown that the observed decrease in activity is due to a degradation of the enzyme itself (LBADH) and not of the co-immobilized cofactor NADP. By the addition of sucrose to the cell extract before immobilization of the enzyme, the half-life of the catalyst preparation (at 40 degrees C) was increased 40 times. The stabilized catalyst preparation was employed in a continuous gas-phase reactor at different temperatures (25-60 degrees C). At 50 degrees C, a space-time yield of 107 g/L/d was achieved within the first 80 h of continuous reaction.
authors.affiliation: Biochemical Engineering, RWTH Aachen University, 52056 Aachen, Germany.
authors.forename: Clara
authors.initials: C
authors.lastname: Ferloni
authors.forename: Matthias
authors.initials: M
authors.lastname: Heinemann
authors.forename: Werner
authors.initials: W
authors.lastname: Hummel
authors.forename: Thomas
authors.initials: T
authors.lastname: Daussmann
authors.forename: Jochen
authors.initials: J
authors.lastname: Büchs
mesh_terms: D000098:Acetophenones / Q000737:chemistry*; D000426:Alcohol Dehydrogenase / Q000737:chemistry*; D001592:Benzyl Alcohols / Q000138:chemical synthesis*; D002384:Catalysis; D004789:Enzyme Activation; D004795:Enzyme Stability; D004800:Enzymes, Immobilized / Q000737:chemistry; D005740:Gases / Q000737:chemistry*; D007700:Kinetics; D010084:Oxidation-Reduction; D044367:Phase Transition; D011786:Quality Control; D013237:Stereoisomerism; D013395:Sucrose / Q000737:chemistry*; D013997:Time Factors
chemical_list: D000098:Acetophenones; D001592:Benzyl Alcohols; D004800:Enzymes, Immobilized; D005740:Gases; D013395:Sucrose; C002017:methylphenyl carbinol; D000426:Alcohol Dehydrogenase; C038699:acetophenone