Environmental Engineering Reference
In-Depth Information
3.3 Applications of Genetic Engineering
Certain challenges inherent in bioreactor operation can be greatly alleviated by the
skillful application of genetic engineering technologies. For example, substrate and product-
based inhibitions are common phenomena which occur when enzyme activities diminish in
the presence of locally high concentrations of certain metabolites. Increasing reactor-mixing
can often alleviate these problems, but diminishing the inhibitory mechanisms genetically can
offer a Because bioengineering for pollution prevention involves relatively low-value
products, requiring optimal bioproces sing for commercial feasibility, improvements in
bioreactor more convenient solution. An example of this approach is presented by Agger and
colleagues, who disrupted the gene responsible for glucose repression so that the glucose
conversion rate did not decrease with increasing glucose concentrations that were, in turn,
needed to work at high biomass concentrations [43]. The ability of genetic engineering to
solve bioreactor-based problems offers a set of great opportunities for improvements in
reactor productivity.
4. Commercialization
Commercial bioreactor usage is growing rapidly, as shown in Figure 4, largely due to
increases in pharmaceutical and food-based biotransformations, which account for over half
and approximately one-quarter of the total biotransformations, respectively [44]. An
important issue for the commercialization of bioreactors for pollution prevention goals is
simply capitalization: entry into established markets for fuels and materials will require large
economies of scale, meaning that production facilities must be constructed on a large scale to
be profitable.
Figure 4. The growth of commercially practiced biotransformations [44]
At the same time, investors are typically reluctant to take risks with newer technologies,
which results in bioreactors producing biofuels and biomaterials that may face significant
initial barriers to market entry. The establishment of pilot plants for both biofuel and
bioplastics production, described in subsequent sections, indicates that these barriers are
nevertheless far from insurmountable.
