Fundamentals of Biological Intervention - Environmental Biotechnology: Theory and Application - page 49

discussed in Chapter 7, this may prove a more difficult proposition, but never-
the-less, one which still remains relevant at least in principle. The typical factors
affecting the use of biological systems in environmental engineering relate to the
nature of the substances needing to be removed or treated and to the localised
environmental conditions pertaining to the particular situation itself. Thus, in
respect of the former, the intended target of the bio-processing must generally
be both susceptible and available to biological attack, in aqueous solution, or at
least in contact with water, and within a low to medium toxicity range. Generally,
the local environmental conditions required would ideally offer a temperature of
20 - 30 ◦ C but a range of 0 - 50 ◦ C will be tolerated in most cases, while an opti-
mum pH lies in the range 6.5 - 7.5, but again a wider tolerance of 5.0 - 9.0 may be
acceptable, dependent on the precise organism involved. For land based appli-
cations, especially in the remediation of contamination or as a component of
integrated pollution control measures, there is an additional common constraint
on the substrate. Typically the soil types best suited to biotechnological inter-
ventions are sands and gravels, with their characteristically low nutrient status,
good drainage, permeability and aeration. By contrast, biological treatments are
not best suited to use in clays or peaty or other soils of high organic content.
In addition, generalised nutrient availability, oxygenation and the presence of
other contaminants can all play a role in determining the suitability of biological
intervention for any given application.
Extremophiles
As has been previously mentioned, in general the use of biotechnology for envi-
ronmental management relies on mesophilic micro-organisms which have roughly
similar environmental requirements to ourselves, in terms of temperature, pres-
sure, water requirement and relative oxygenation. However, often some of their
abilities, which are directly instrumental in enabling their use in this context,
arose in the first instance as a result of previous environmental pressures in
the species (pre)history. Accordingly, ancient metabolic pathways can be very
valuable tools for environmental biotechnology. Thus, the selective advantages
honed in Carboniferous coal measures and the Pleistocene tar pits have produced
microbes which can treat spilled mineral oil products in the present and methano-
genesis, a process developed by the Archae during the dawn of life on Earth,
remains relevant to currently commonplace biological interventions. Moreover,
some species living today tolerate extreme environments, like high salinity, pres-
sures and temperatures, which might be of use for biotech applications requiring
tolerance to these conditions. The Archaea (the group formerly known as the
archaebacteria and now recognised as forming a distinct evolutionary line) rank
amongst their numbers extreme thermophiles and extreme halophiles in addition
to the methanogens previously mentioned. Other species tolerate high levels of
ionising radiation, pH or high pressures as found in the deep ocean volcanic
vents known as 'black smokers'.