Pollution and Pollution Control - Environmental Biotechnology: Theory and Application - page 85

Biomimetics
The idea of sustainable development is inherent in the science of biomimetics,
so it is unsurprising that there are some excellent potential applications of bio-
substitution in this field and perhaps one of the best of these is to be found
in attempts to defeat aquatic, and especially marine, biofouling. The unwanted
accumulation of various forms of life, including algae, microorganisms and sessile
animals on submerged structures is a serious economic and practical nuisance
to a number of industries. According to US Naval sources, micro-fouling by
surface-adhering biofilms can increase drag on a warship by up to 20%, while
the presence of macro-fouling by barnacles and other larger organisms can add
more than 60% overall (ONR, 2009). This has been calculated as leading to
as much as a 40% increase in fuel consumption and up to 10% reduction in a
ship's speed. US Navy estimates have put the extra cost that this all entails in
supplementary fuel and maintenance at an additional $1 billion per year (ONR,
2009). It is, however, not an issue simply affecting warships. Aside of hulls, any
submerged or partially submerged structure, from cables and pipelines to drilling
rigs, can suffer biofouling although obviously the relative economic importance
it assumes varies.
Conventional anti-fouling treatments rely on the biocidal action of various
agents to kill organisms attempting to attach themselves, but they are essen-
tially indiscriminate and tend to both leach and accumulate in the ecosystem,
where their toxicity may prove a threat to other non-target species. A common
example, tributyltin (TBT), for instance, has been shown to lead to genital abnor-
malities at concentrations as low as 1 ng/l in the dog whelk Nucella lapillus and
at 20 ng/l, normal shell formation in the Japanese oyster Crassostrea gigas is
disrupted. Unsurprisingly, it has been described as the most toxic substance ever
introduced into the marine environment (Sonak et al ., 2009). In September 2008
the International Convention on the Control of Harmful Anti-Fouling Systems
on Ships (AFS Convention) came into force in September 2008, banning the
application or re-application of TBT and other organotin compounds, but clearly
the need for effective anti-fouling remains. Other chemical based systems have
been established to fill the void, and others suggested including, interestingly
from a biotechnological standpoint, the possible use of secondary metabolites
from cyanobacteria, such as the carboline alkaloid, nostocarboline, isolated from
Nostoc (Gademann, 2007). As prolific producers of highly chemically diverse
secondary metabolites (Smith and Doan, 1999), the cyanobacteria have long been
regarded as a potentially valuable source of active anti-fouling agents (Dahms,
Ying and Pfeiffer, 2006). However, developments in biomimicry could play a
significant role in shaping the future of next-generational anti-fouling products
and possibly other surface coatings where effective microbial growth inhibition
is also essential.
Unlike marine species such as whales and turtles which are prone to barnacle
encrustation, sharks are characteristically untroubled by biofouling and studies
of their skin have established that its unique texture coupled with its inherent