Figure 9.8 Comparison of thermal
stability of C. rugosa lipase adsorbed
onto Chromosorb P for a
transesterification between n-propanol
and methyl propionate in gas/solid
system and in liquid system at 70°C.
Alcohol and ester were at the same
molar ration in both systems and liquid
system was previously prequilibrated
at the same aw (0.7 in this case).
APPLICATION OF SOLID/GAS CATALYSIS: THE ALCOHOL
DEHYDROGENASE OF BAKER’S YEAST DEAD CELLS
Many aldehydes and alcohols are used in the agro-industries for their flavouring
properties. The majority, of flavors are produced by chemical means or by extraction
from a natural product. For these reasons, an alternative approach was chosen for
producing such compounds, but because purified alcohol dehydrogenase immobilised or
co-immobilised with its cofactor was not economically viable for industrial application,
the ability of whole baker’s yeast dead cells to reduce aldehyde and oxidise alcohol
vapors was already being studied (Hwang and Trantolo, 1993; Hwang and Park, 1994). In
the following example, the reduction of hexanal with baker’s yeast to prepare hexanol
was chosen as the reaction model. In addition, cofactor NADH, H+ was regenerated with
a second substrate, ethanol. The oxidized NAD is reduced back to NADH, H+ by baker’s
Multiphase bioreactor design 276