ý.,,: V. ý ýý . - Nottingham eTheses - University of Nottingham

depths of each lake from which they were isolated suggests that some AFP active species
evolved AFP activity as a selective advantage over other non-AFP active bacteria,
suggesting that they were competitively excluded from environments which were warmer
and had less freezing stress. However, the presence of AFP active species in various
may also be able to successfully compete for nutrients in parts of the lake where AFP
activity is redundant.
Including the 19 AFP active environmental isolates thus far described, a further
847 cultured isolates were maintained during the current study. The potential
biotechnological resource is therefore considerable, as these psychrotrophic and
psychrophilic bacterial species are possible sources of novel biochemical compounds.
Not only have a series of bacterial species producing possibly novel AFPs been isolated
and characterised, but also a huge potential reservoir of cold tolerant enzymes (e. g.
proteinases, lipases and cellulases), polyunsaturated fatty acids (for food additives) and
various pharmaceuticals (Feller et al., 1996; Feller & Gerday, 1997; Russell &
Hamamoto, 1998; Gerday et al., 2000) is now available. The potential use of AFPs in
industry is also well documented, e. g. in preservation of frozen foods, such as meat and
ice cream (Griffith & Ewart, 1995; Feeney & Yeh, 1998), cryopreservation of living
tissue (Wu & Fletcher, 2000), maintenance of ice slurries as cooling agents in industrial
plants (Inada et al., 2000) and protection of freeze-intolerant food animals and
agricultural crops (Feeney & Yeh, 1993). The development of the AFPs from the current
study into working biotechnological products will require considerable future research to
identify and purify the proteins with antifreeze activity, understanding of post-
translational modifications and then research the possible applications of these purified
proteins. Bacterial AFPs from the current study could provide a readily exploitable
source of AFP. The bacterial species involved require no specific growth requirements
for the production of AFP activity (save those reported in the current study) and as such
could be easily produced on an industrial scale, especially if further research was
conducted into the optimisation of AFP yield from bacterial cultures.
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