expression. In this case, the synthetic genes are assembled in a host organism
suitable for industrial production of the said chemical, but a more used approach is
adaptation of enzymes by modifying substrate specificity in a given metabolic path
to promote the formation or consumption of a metabolite of interest. One of the
most demonstrative works in the development of an L-homoalanine producing
strain developed by introducing a synthetic pathway with a modified glutamate
dehydrogenase, this enzyme has been modified to convert 2 ketobutyrate into the
nonnatural amino acid L-homoalanine (Leonard et al. 2010; Zhang et al. 2010).
Synthetic biology makes feasible the expression of several cellulases, lipases,
and esterases that can be regulated in a coordinated way in any recombinant wellknown organism as Saccharomyces o E. coli. This approach is very similar to
nature, where a single organism expresses several combinations of cellulases that
wok in a synergic system. Production of several enzymes normally results in a
much higher level of degrading activity. The modular nature of synthetic biology
allows the combinatorial assay of enzyme genes of different origin and activity,
which can then be screened against several lignocellulose substrates for the most
effective degradation ability for a given substrate. These experiments can be used
to generate databases of heterologous gene degrading abilities against any given
substrate (Fench 2009). Decreasing costs of synthetic DNA results in a cheaper
and simpler way to assemble complex multigene systems. This flexibility has the
potential to allow the generation of useful organisms from different origins to
obtain an IBPM, thus making the conversion of biomass into chemicals or biofuels
a reality.
7.7.4 Conversion of Lignocellulosic Biomass into ValueAdded Products
Conversion of biomass into valuable products may begin with biofuels as ethanol,
biodiesel methane, and hydrogen. All these molecules already have a large market
since they are used as chemical feedstock and are used extensively by Brazil and
USA as primary fuel or additive (Kerr and Service 2005). Production of ethanol
from food grade materials is an expensive substitute for oil-based fuels, and one of
the most urgent issues that need to be addressed by new technologies and production from lignocellulose wastes is the best alternative (Kumar et al. 2008).
Methane and hydrogen as biofuels exemplify the best opportunity to show how
a integrated process may work, both molecules can be produced as a by-product of
cellulose waste or municipal sewage water treatment. There are advances in
production of methane from a wide range of lignocellulose biomass. Maheshwari
et al. (2000) and Wang et al. (2011) demonstrate the feasibility of production of
hydrogen in an integrated process that includes lignocellulose degradation and
hydrogen production by microbial fuel cells.
7 Integral Management of Lignocellulosic Biomass by Biorefining
247
suitable for industrial production of the said chemical, but a more used approach is
adaptation of enzymes by modifying substrate specificity in a given metabolic path
to promote the formation or consumption of a metabolite of interest. One of the
most demonstrative works in the development of an L-homoalanine producing
strain developed by introducing a synthetic pathway with a modified glutamate
dehydrogenase, this enzyme has been modified to convert 2 ketobutyrate into the
nonnatural amino acid L-homoalanine (Leonard et al. 2010; Zhang et al. 2010).
Synthetic biology makes feasible the expression of several cellulases, lipases,
and esterases that can be regulated in a coordinated way in any recombinant wellknown organism as Saccharomyces o E. coli. This approach is very similar to
nature, where a single organism expresses several combinations of cellulases that
wok in a synergic system. Production of several enzymes normally results in a
much higher level of degrading activity. The modular nature of synthetic biology
allows the combinatorial assay of enzyme genes of different origin and activity,
which can then be screened against several lignocellulose substrates for the most
effective degradation ability for a given substrate. These experiments can be used
to generate databases of heterologous gene degrading abilities against any given
substrate (Fench 2009). Decreasing costs of synthetic DNA results in a cheaper
and simpler way to assemble complex multigene systems. This flexibility has the
potential to allow the generation of useful organisms from different origins to
obtain an IBPM, thus making the conversion of biomass into chemicals or biofuels
a reality.
7.7.4 Conversion of Lignocellulosic Biomass into ValueAdded Products
Conversion of biomass into valuable products may begin with biofuels as ethanol,
biodiesel methane, and hydrogen. All these molecules already have a large market
since they are used as chemical feedstock and are used extensively by Brazil and
USA as primary fuel or additive (Kerr and Service 2005). Production of ethanol
from food grade materials is an expensive substitute for oil-based fuels, and one of
the most urgent issues that need to be addressed by new technologies and production from lignocellulose wastes is the best alternative (Kumar et al. 2008).
Methane and hydrogen as biofuels exemplify the best opportunity to show how
a integrated process may work, both molecules can be produced as a by-product of
cellulose waste or municipal sewage water treatment. There are advances in
production of methane from a wide range of lignocellulose biomass. Maheshwari
et al. (2000) and Wang et al. (2011) demonstrate the feasibility of production of
hydrogen in an integrated process that includes lignocellulose degradation and
hydrogen production by microbial fuel cells.
7 Integral Management of Lignocellulosic Biomass by Biorefining
247