Environmental Engineering Reference
In-Depth Information
late summer-collected soil samples, are notable. This success demonstrates that
sampling in extreme or highly remote areas may not be required for the isolation of
strains with these properties. With the aid of these selective techniques, it may even
transpire that these properties are not quite as rare as we had once assumed.
Why is it important to identify microbes with psychrophilic adaptations? For
the basic scientist, knowledge about survival under extreme conditions and
insights into the evolution of these resistant traits will suffice. However, there
are also other reasons to identify these organisms. Such microbes offer the
prospect that proteins with interesting properties such as antifreeze and ice
nucleating activities can be more readily identified. In addition, these isolates
are likely to produce enzymes that are sufficiently active at low temperatures to
be useful for applications under extreme conditions. Examples could include the
bioremediation of spills and polluted sites in the far north and on the sea bed.
Nucleation of freezing at consistent temperatures close to 08C could save energy
costs for various industrial chilling processes including frozen food production,
freeze-concentration and food preservation and transportation [46]. Strains of
P. borealis are classified as plant beneficial bacteria since certain soil-borne plant
pathogens are suppressed [47], and our ice-affinity recovered P. borealis showed
impressive nucleation activity (S. Wu and V.K. Walker, unpublished). Indeed,
the ice nucleation activities are so high that our isolate approaches that of
commercial snow making preparations derived from P. syringae, a plant patho-
gen [36]. Thus, there may be applications, including cloud seeding over agricul-
tural areas, where the use of P. borealis-derived nucleators could be preferable.
However, amongst the most urgently needed products are environmentally
friendly gas hydrate inhibitors. This need is likely to become acute within the
next two decades as the search for energy drives the industry to deeper waters
and under the permafrost. Thus it is our hope that products isolated from
psychrophiles will prove useful for the inhibition of gas hydrates. As previously
indicated, AFPs inhibit the formation of gas hydrates [3, 4] and should repre-
sent ideal 'green inhibitors'. However, they currently cannot be produced in the
volumes required for their practical application in the field. AFPs can be
isolated from fish and insect serum, but these sources do not represent a reason-
able option. Recombinant DNA technology has allowed the production of
many foreign products in simple cells, but in this case, neither E. coli nor
yeast cells can efficiently and accurately fold the same AFPs [48, 49] that are
the most active against hydrates.
The ability to screen psychrophiles for ice-associating properties should
permit the identification of products that can also act as hydrate-associating
molecules in order to change the kinetics of gas hydrate formation. Preliminary
experiments in our labs (E. Huva, J.A. Ripmeester and V.K. Walker, unpub-
lished) suggest that microbes with antifreeze as well as ice nucleating activities
can influence hydrate formation. This is a significant finding since it represents
a glimmer of hope that an affordable, environmentally benign method to
control and inhibit hydrate formation may be found in microbes isolated by
the selection techniques described in this chapter. Indeed, challenging and
