Bakerʹs yeast activity in an organic solvent system

The bakerʹs yeast mediated reduction of ethyl 3-oxobutanoate-3-13C in hexane was conducted in an NMR tube at 20°C and a 13C NMR spectrum recorded each hour. A plot of relative peak intensity against time allowed the progress of the reaction to be monitored. A series of reactions was carried out in which the yeast was pretreated with the organic solvent system for 3, 6, 12 and 24 h prior to the addition of the substrate. From the initial rate of these reactions it was determined that in hexane the enzyme activity remained constant for about 12 h and then rapidly decreased until after 24 h very little activity remained. The reaction was also carried out at 10°C and 30°C. At the lower temperature, the reaction was slower but enzyme activity was maintained for more than 60 h, while at 30°C the enzyme activity had ceased after 8 h.