product assortment including not only petroleum-based products but a new variety
of products not available from oil refineries (Kamm and Kamm 2004; National
research council 2000). These refineries are yet to be developed. Actually there are
Phase I refineries where food grade grains are converted into ethanol in a fixed
processing system, however, they have no flexibility and cannot be used for other
purposes; Phase II refineries use feedstock grain and are capable to produce
diverse end-products according to demand, as bioplastics, glucose, oil, and ethanol
(Nonato et al. 2001). A Phase III biorefinery must be able to produce several endproducts on demand, but much more important, it must be able to process several
different feedstocks predominantly lignocellulose wastes of many sources (Kamm
and Kamm 2004).
The complications that hinder the successful achievement of this idea are
presented in the following example. In the initial process to obtain ethanol from
cellulose biomass, a lignin disrupted biomass is treated with fungal cellulases to
release glucose. The glucose is then fermented conventionally by Saccharomyces
cerevisiae to yield ethanol (Lynd et al. 2002); this process is complex and presents
several problems, the most important of which is the inhibition of cellulose degradation by accumulation of end-products. To overcome these problems, simultaneous saccharification and fermentation has been developed. In this process,
cellulose degrading enzymes are added to the fermenting bioreactor, so glucose is
consumed as fast as it is produced. This improves the process in two ways; first,
avoiding cellulose degrading end-product inhibition, and at the same time catalytic
rate of all enzymes is improved as there is no buildup of by-products on the media,
but as a result other challenges arise in the new process such as the accumulation
of pentoses released in the culture media that wild yeast is incapable to use as
fermentable sugars from these two solutions has been presented a recombinant S.
cerevisiae able to use pentoses and Klebsiella strain that is naturally able to use
xylose and arabinose developed as a high yield alcohol producer (Zhou et al. 2001;
Hughes et al. 2009).
This example illustrates two additional points, an organism able to degrade
lignocellulosic biomass may be unable to grow in an efficient well-known production system or produce a valuable molecule in a cost effective process. On the
other hand it is possible to have a very good producing organism incapable to use
lignocellulosic degradation material proficiently. Therefore, the requirement to
find what French (2009) calls the Ideal Biofuel Producing Microorganism (IBPM)
is according to this a suitable organism must be able to: (1) hydrolyze cellulosic
material effectively with minimal preprocessing, (2) it must be able to convert
sugar released by lignocellulosic degradation into molecules useful as fuels, or
chemical industry feedstocks, (3) it must be able to produce those molecules at a
high concentration without poisoning itself, and (4) it must be capable of rapid
growth in a bioreactor and suitable to be used in an industrial context (French
2009).
New technologies are making possible the discovery and development of
improved enzymes, with novel enzymatic activities, multiple catalytic sites, and
better suited to act in the harsh environments of industrial process. Searching for
7 Integral Management of Lignocellulosic Biomass by Biorefining
245
of products not available from oil refineries (Kamm and Kamm 2004; National
research council 2000). These refineries are yet to be developed. Actually there are
Phase I refineries where food grade grains are converted into ethanol in a fixed
processing system, however, they have no flexibility and cannot be used for other
purposes; Phase II refineries use feedstock grain and are capable to produce
diverse end-products according to demand, as bioplastics, glucose, oil, and ethanol
(Nonato et al. 2001). A Phase III biorefinery must be able to produce several endproducts on demand, but much more important, it must be able to process several
different feedstocks predominantly lignocellulose wastes of many sources (Kamm
and Kamm 2004).
The complications that hinder the successful achievement of this idea are
presented in the following example. In the initial process to obtain ethanol from
cellulose biomass, a lignin disrupted biomass is treated with fungal cellulases to
release glucose. The glucose is then fermented conventionally by Saccharomyces
cerevisiae to yield ethanol (Lynd et al. 2002); this process is complex and presents
several problems, the most important of which is the inhibition of cellulose degradation by accumulation of end-products. To overcome these problems, simultaneous saccharification and fermentation has been developed. In this process,
cellulose degrading enzymes are added to the fermenting bioreactor, so glucose is
consumed as fast as it is produced. This improves the process in two ways; first,
avoiding cellulose degrading end-product inhibition, and at the same time catalytic
rate of all enzymes is improved as there is no buildup of by-products on the media,
but as a result other challenges arise in the new process such as the accumulation
of pentoses released in the culture media that wild yeast is incapable to use as
fermentable sugars from these two solutions has been presented a recombinant S.
cerevisiae able to use pentoses and Klebsiella strain that is naturally able to use
xylose and arabinose developed as a high yield alcohol producer (Zhou et al. 2001;
Hughes et al. 2009).
This example illustrates two additional points, an organism able to degrade
lignocellulosic biomass may be unable to grow in an efficient well-known production system or produce a valuable molecule in a cost effective process. On the
other hand it is possible to have a very good producing organism incapable to use
lignocellulosic degradation material proficiently. Therefore, the requirement to
find what French (2009) calls the Ideal Biofuel Producing Microorganism (IBPM)
is according to this a suitable organism must be able to: (1) hydrolyze cellulosic
material effectively with minimal preprocessing, (2) it must be able to convert
sugar released by lignocellulosic degradation into molecules useful as fuels, or
chemical industry feedstocks, (3) it must be able to produce those molecules at a
high concentration without poisoning itself, and (4) it must be capable of rapid
growth in a bioreactor and suitable to be used in an industrial context (French
2009).
New technologies are making possible the discovery and development of
improved enzymes, with novel enzymatic activities, multiple catalytic sites, and
better suited to act in the harsh environments of industrial process. Searching for
7 Integral Management of Lignocellulosic Biomass by Biorefining
245