Biorefineries using waste – production of energy and chemicals from biomasses by micro-organisms - Biomass as Energy Source: Resources, Systems and Applications - page 255

13.12.4 Local products of microbial metabolism with global impacts
As a consequence of local energy production, local small-scale production of goods is encour-
aged. In agriculture, this means safer food production with less transportation. Instead of huge
industrial plants destroying the balance in their environment, the local microbial biotechnology
facilitates energy and food production with small industries for local communities. Such pat-
tern has turned out successful in Israel, where agricultural kibbutzim have provided grounds for
high-tech enterprises.
A bioprocess plant resembles the digestive tract of humans or animals. Ruminants, for example
are converting the cellulose-containing plant materials into animal biomasses with high speed.
This process is effectively made possible by the microbes and their enzymes. The ruminants have
specific microflora in their digestive tract (Madigan et al. , 2003). In case of human alimentary
tract with a very distinctive flora, being also dependent on the health status of the individual, the
reactions resemble the processes carried out in the biorefineries (Hakalehto, 2012).
In the acidic gastric fluids and on the epithelial surfaces the microbes need specific survival
strategies as like the Helicobacter pylori bacterium, which is protecting its surface colonies on the
epithelia by ureolytic enzymes, which balance the pH (Cullen et al. , 2011). Even the lactic acid
bacteria could survive in the stomach of 13 healthy individuals as indicated by the endoscopic
samples enriched in the PMEU (Hakalehto et al. , 2011b). After the low pH conditions of the
stomach, the chime is pumped in pulses into duodenum and rapidly neutralized (Hakalehto, 2012).
There the facultative bacteria constitute a balanced milieu for maintaining their own communities
in relatively stable pH and osmotic conditions (Hakalehto et al. , 2008, 2013). This is the basis for
enzymatic hydrolysis of the food macromolecules and later on the starting point of the column of
microorganisms along the intestinal tract. This ecosystem is producing the most of its biomass in
the colon, where most of the nutrients required for human consumption have been uptaken earlier
(Hakalehto, 2012). The reaction sequences inside our digestive tract could give an inspiration for
designing biotechnical applications.
The various ways for different microorganisms to produce their energy are:

• respiration

• fermentative pathways

• anaerobic respiration

• photosynthesis.

Besides the fulfilment of their energy needs, the microbes need also carbon source, minerals,
trace elements, growth factors, vitamins etc. Those strains, which get along without organic raw
materials are called autotrophs, whereas the strains utilizing organic matter, or biomasses, are
heterotrophs. The photosynthetic algae or bacteria, for example, belong to the former group.
The heterotrophs, in turn, circulate the biomass substances, acquiring their energy supplies by
liberating the energies from the chemical bonds in the organic matter. This is their catabolism.
As byproducts, different microbes also produce and emit lots of various substances, which are
exploitable in the biotechnological industries. In the waste treatment, these metabolic capabilities
of the microorganisms can be exploited.
The vast capacity of the microbial metabolism is multiplied with the use of the mixed cultures.
In fact, the term “co-metabolism” means the joint action and outcome of the different microbial
species in a co-culture on a particular substance, or raw material, for degrading and utilizing
substances otherwise difficult for the processes. The co-metabolism is resulting in enhanced and
extended biochemical products. For example, some recalcitrant are most often not degraded by
any single microbes, but with a selected mixed cultures (Quan et al. , 2004).
The current improvements in the biorefinery technologies are recently reviewed (El-Hawegi and
Stuart, 2012). Integrated processes offer more economic feasibility and lower the environmental
consequences. As it has been a well-known fact that biotech product facilities could be modified
or converted suitable for variable process needs with relatively low cost, this increases flexibil-
ity of this industrial discipline. The biorefineries could be seen as fields of different biomass