Metabolic and Process Engineering of Clostridium Tyrobutyricum for the Optimization of Butanol Production

As the demand for alternative fuel sources has increased,
there has been renewed interest in the production of butanol from
microorganisms such as the bacterium Clostridium
tyrobutyricum. Butanol is a promising alternative due to its ability to
integrate easily into current systems, however the production process must be
optimized before commercial application becomes viable. The production of
butanol from C. tyrobutyricum is
examined and altered by implementing techniques of metabolic engineering.
Multiple plasmids have been constructed and used to create high performance C. tyrobutyricum mutants by improving
the central butanol formation pathway and decreasing byproducts.

Furthermore, the fermentation process was examined and the
knowledge acquired will facilitate more effective fermentation in the future.
One of the main goals of butanol fermentation using microorganisms is to
utilize lignocellulosic materials due to their availability and low cost.
However, the lignin, cellulose, and hemicellulose cannot be consumed by Clostridium species without
pretreatment. The pretreatment process releases microbial inhibitors that
reduce the fermentation yield and productivity, including weak acids,
derivatives of furan, and phenolic compounds. The inhibitory effects of two
representative compounds, furfural and phenol, have been examined in batch
fermentations of C. tyrobutyricum for
butanol production. Both cell growth and butanol formation were sensitive to
inhibitor concentrations, and resistance under low concentrations was observed,
indicating that the inhibition effects can be alleviated or avoided through
detoxification of the pretreated biomass. Future work will focus on optimizing
the construction and fermentation of high performance mutants to generate high yields
of butanol.