Environmental Engineering Reference
In-Depth Information
Chapter 2
Screening Microbes for Ice-Associating Proteins
with Potential Application as 'Green Inhibitors'
for Gas Hydrates
V.K. Walker, S.L. Wilson, Z. Wu, D.N. Miao, H. Zeng, J.A. Ripmeester
and G.R. Palmer
Abstract The survival of microbes at low temperatures is important for our
understanding of overwintering and the mechanisms of stress adaptation.
However, such organisms also deserve attention for the potential they hold as
sources of products to address practical problems and for providing environ-
mentally responsible options. One such threat to the ecosystem is the danger
posed by the unexpected and catastrophic formation of gas hydrates in pipe-
lines during drilling operations, transport and throughout fractionation. The
most popular chemical gas hydrate inhibitors are themselves toxic, making the
discovery of new 'green' hydrate inhibitors a high priority. Recently, we have
shown that antifreeze proteins, which inhibit ice growth, can also inhibit gas
hydrate formation. Although current sources of these proteins are not sufficient
for these applications, we believe that microbial products can be a part of
the solution to this challenge that poses a special threat to both marine and
northern ecosystems. Here, we outline strategies and methods for the isolation
of microbes with these properties.
Keywords Gas hydrates
gas exploration
antifreeze proteins
ice nucleators
freeze-thaw
ice affinity
overwintering
2.1 The Gas Hydrate Problem
Gas hydrates are made of crystalline ice-like cages of water that house small
gases such as methane or propane, and form when temperature and pressure
conditions are favorable. They are found naturally in the permafrost regions as
well as near the continental shelves under the sea. In all, world wide deposits of
gas hydrates are estimated at
200 million trillion cubic feet. Gas hydrates will
undoubtedly be used to offset the world's energy thirst within the next couple of
decades since they represent a vast reservoir of potential energy and wealth,
