Environmental Engineering Reference
In-Depth Information
Advances in sensing technologies are urgently needed, especially in the design of
bioprocesses for commodity products where efficiency is paramount, and this area should be
considered a top priority within bioengineering for pollution prevention.
3. Research Priorities
Because bioengineering for pollution prevention involves relatively low-value products,
requiring optimal bioprocessing for commercial feasibility, improvements in bioreactor
technology should be a high priority in general in this field. In addition, several areas are
worthy of specific mention:
3.1. Sensing
Real-time sensing of gases and aqueous metabolites is of central importance because it
allows or has the potential to facilitate model validation, development of descriptive kinetic
expressions, and real-time process control based on sensor feedback alone and in combination
with model predictions. Biosensors suitable for monitoring bioconversions in bioreactors
have been previously identified as a bottleneck in the development of high-volume, low-cost
processes [42], indicating that the development of promising emerging technologies should be
encouraged in every instance possible.
3.2. Modeling
In process design and optimization, the utility of a mathematical model lies in its ability
to predict the operating characteristics in regions for which experimental data do not exist.
Present kinetic models generally do not allow such procedures in great detail. Detailed kinetic
models are also useful for capturing the dynamic responses of bioreactors to external stimuli,
a set of important concerns in process control. Accordingly, a promising area of investigation
is the development of more-detailed structural models that capture the salient features of
complete metabolic pathways through the integration of biochemistry, molecular biology, and
computational techniques. In particular, new approaches to structural kinetic modeling that
include transcriptional and post-translational regulatory effects are needed.
In addition, new developments are needed in computational methods to capture effects of
turbulence in bioreactors, effects of shearing and mechanical stresses on cellular growth and
death, and the non-Newtonian nature of cellular media. These must involve multi-scale
modeling to capture details at small spatial scales and must also be able to transfer relevant
information to lower-resolution models that describe greater volume and time scales. CFD
models are now able to establish hydrodynamic profiles among different zones of a reactor
and could serve as the basis for such models, describing concentration and temperature
gradients both instantaneously and over time. Such models could be extended to bridge
length, volume, and time scales, linking detailed calculations at smaller scales or in critical
areas with lower- resolution models that track averaged quantities. Given recent and
continuing increases in inexpensive computing power, such models could contribute greatly
to reactor optimization. In addition, they have the potential to guide the scale-up of industrial
processes by revealing important mass and heat transfer limitations as reactor configurations
are changed.
