Baker's yeast mediated bioreduction: Practical procedure using EtOH as energy source

Efficient anaerobic whole cell stereoselective bioreduction with recombinant saccharomyces cerevisiae

“…When performed under nonoptimized conditions, the whole cell bioreduction system sometimes suffers from drawbacks such as low yield, substrate inhibition, and low reduction rate (Hage et al, 2001;Katz et al, 2002;Zmijewski et al, 1997). Carbonyl reduction is affected by pH (Hage et al, 2001;Katz et al, 2002;Patel et al, 1991;Zmijewski et al, 1997), oxygenation (Kometani et al, 1991(Kometani et al, , 1993a, temperature (Katz et al, 1996;Patel et al, 1991), initial substrate concentration (Hage et al, 2001;Katz et al, 1996Katz et al, , 2002Zmijewski et al, 1997), ratio between yeast/cosubstrate/substrate , mode of bioreduction (batch versus fed-batch system) (Chin Joe et al, 2001;Kometani et al, 1993b), and choice of yeast species (Botes et al, 2002;Katz et al, 1996;Patel et al, 1991;Yasohara et al, 1999;Zmijewski et al, 1997).…”

“…Reductase(s) performing the reduction are usually cytosolic, accept many substrates, and require the reduced cofactor NADPH, which is oxidized to NADP + (Costello et al, 2000;Jez and Penning, 2001;Kallberg et al, 2002;Katz et al, 2003;Maser, 1995;Stewart et al, 2001;Sybesma et al, 1998). During the reduction process the cofactor is recycled as long as the cosubstrate is present, but, when depleted recycling stops, with a concomitant termination of bioreduction Kometani et al, 1991;Zmijewski et al, 1997). Thus, there is a need to balance the rates of the two reactions in the whole cell reduction system, and in an optimal system the two rates are equal.…”

“…In batch conditions, large amounts of glucose are required because glycolysis is much faster than the reduction rate, leading to low cosubstrate yield (formed chiral alcohol product/ consumed cosubstrate) and an accompanying high byproduct formation . Ethanol is consumed much slower than glucose and, therefore, only small amounts are needed with concomitant low byproduct formation (Kometani et al, 1991). Ethanol has been used successfully to produce chiral alcohols with CO 2 as the only byproduct (Kometani et al, 1991(Kometani et al, , 1993a(Kometani et al, , 1993b(Kometani et al, , 1994(Kometani et al, , 1995.…”

Diltiazem Synthesis, Microbial Asymmetric Reduction

“…Although it is widely accepted that sugar is essential as an energy source, the use of ethanol as the energy source has also been considered because it is clean and efficient compared with sugar (15,(26)(27)(28)(29)(30).…”

NADPH-dependent Reduction of Ethyl Acetoacetate Coupled with Ethanol Oxidation inKloeckera magna

“…The concentrations of EA, E3-HB, ethanol, and acetic acid were measured by gas-liquid chromatography as described. 6) The specific reduction rate by each yeast strain was calculated from the concentration of E3-HB after 8 h per unit weight of dry cells. The actual specific reduction rate in the presence of ethanol or glucose was obtained by deducting the specific reduction rate of the control without an energy source from the corresponding specific reduction rate and is represented as (E-N) or (G-N) [mmol/h/g-dry-cellJ, respectively.…”