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.

Optimization of adsorptive immobilization of alcohol dehydrogenases

“…Obviously, sucrose occupies the adsorption sites on the support material and consequently less sites on the support are available for protein binding. Ferloni et al (6) have shown that enzyme preparations prepared with sucrose have markedly improved stability under reactive gas phase conditions.…”

“…Unfortunately the operational instability of ADHs in aqueous solution limits their widespread industrial application (3,4). Application of ADHs in non-conventional media such as organic solvents and in a gas/solid system (enzymatic gas phase system) could overcome some of the problems associated with the ADH instability in aqueous media (5,6). However, the use of enzymes in powder form in non-conventional media may lead to mass transfer limitations.…”

“…Therefore, the regeneration of the cofactor (NADH or NADPH) has to be carried out using a co-substrate. For alcohol dehydrogenases, short chain aliphatic alcohols are typically applied (5,6). Initial results on the application of immobilized LBADH in gas-phase catalysis using substrate-coupled cofactor regeneration are reported in the paper of Ferloni et al (6).…”

Production of (R)‐1‐phenylethanols through bioreduction of acetophenones by a new fungus isolate Trichothecium roseum

“…[25][26][27] In comparison, Trichothecium roseum is sensitive to the position and electronic effect of the substituent. Thus, the derivatives 1b-d and 1o-p did not afford the corresponding alcohols 2 ( Table 2, entries 2-4, and [13][14]; however, in contrast to this observation, Aspergillus niger and Alternaria alternata are not substrate structure-dependent reducers. While Trichothecium roseum exhibits R selectivity in all cases, Aspergillus niger and Alternaria alternata do not show any preference in enantioselectivity.…”

Dehalogenation of gaseous 1‐chlorobutane by dehydrated whole cells: Influence of the microenvironment of the halidohydrolase on the stability of the biocatalyst

“…Indeed, it presents many advantages compared to other enzymatic systems (i.e., liquid, mono or biphasic ones): (i) mass transfers are more efficient at the solid/gas interface, (ii) isolated enzymes and cofactors are usually more stable due to a restricted water availability, (iii) problem of solubility of substrates and products do not exist, and (iv) the use of solvent can be avoided Legoy, 1993, 1995a). It has been used with enzymes such as lipases and esterases (Lamare and Legoy, 1993;Lamare et al, 2001), oxydo-reductases (Ferloni et al, 2004;Trivedi et al, 2006a,b), dehalogenases (Dravis et al, 2000(Dravis et al, , 2001, a lyase, and a decarboxylase (Spiess et al, 2007).…”