Environmental Engineering Reference
In-Depth Information
glucose as substrate, in contrast to the conventional synthesis that requires benzene or other
aromatic solvents [20].
Bioengineering for pollution prevention is an emerging area of both an intellectual
endeavor and an industrial practice. The economic driving forces, the importance of
feedstock, and the scale of production all distinguish this arena of biotechnology from the
pharmaceutical and nutritional sectors. While fossil fuel-based economies typically evolve
from a relatively low-value commodity (e.g., kerosene for lighting) to intermediate-value
materials (gasoline, plastics) and ultimately to valuable specialty chemicals (cosmetics,
pharmaceuticals), it appears that the biobased economy is progressing from high-value
products (pharmaceuticals) to those of intermediate value (industrial catalysts, plastics). As
biotechnology evolves and matures, the production of large-scale, relatively low-value
products such as fuels is becoming increasingly attractive and economically feasible.
B.
C
URRENT
C
HALLENGES
1. Cellulose Stability
The greatest impediment to widespread application of bioengineering for production of
commodities is currently the general absence of low-cost processing technologies for
biomass. Challenges associated with the conversion of plant biomass into useful products are
dominated by the chemical stability of cellulose within biomass (Figure 1), causing it to resist
modification and therefore require valuable enzymes or other catalysts, as well as special
processing conditions [21].
Advances are therefore greatly needed in both enzymatic and non-enzymatic biomass
pretreatment technologies, as well as in the development of efficient product-producing
microbes and fermentation bioreactor technologies, the latter of which would directly benefit
non-biomass-consuming processes as well.
The generation of high-value coproducts has the potential greatly to offset expenses of
processing any feedstock, showing that exploration of the diversity of products that a process
or feedstock can yield is also of central importance to the realization of true, profitable,
economically resilient biorefineries.
2. Engineering Optimal Organisms
Genetic and metabolic engineering techniques are now being used to address the
mivrobial and enzymatic problems of biocommodity production from hundreds of different
angles. The central goal, in virtually all cases, is the development of organisms that can use
low-cost substrates, give high product yields, and/or exhibit robustness in temperature and pH
extremes characteristic of many industrial environments.
The rapidity of development of techniques for manipulation and/or analysis of gene
sequences and expression patterns, as as the exponential rate of accumulation of genetic
information about numerous industrial microorganisms, are enormous forces propelling the
field of bioengineering forward [22].
