During the 1980s and 1990s substantial progress was made in
the development of genetic systems for the solventogenic Clostridia
used in ABE fermentation, which would allow for the development
of strains with improved fermentation characteristics [4]. However,
the major hurdles to overcome before an economically competitive
biological process could be reintroduced were: the high
cost of the substrate, the low fermentation product concentration
(about 2% because of solvent toxicity to the micro-organism), and
the high product recovery cost (distillation has been used in the
past). A number of factors presently stimulate the present interest
in technology development of biobutanol production. These include
the current instability of oil supplies from the Middle East
[5], a readily available supply of renewable agriculturally based
biomass [6], and the call for reduction of greenhouse gas emissions
[7]. Ultimately, a revival of the ABE fermentation process is dependent
on favorable economic conditions relative to petrochemicalbased
processes [8].