In adapting to low-temperature environments, microorganisms have shown a
number of physiological and biochemical changes. For this reason, they are believed
to possess enzymes with various properties related to low temperature adaptations.
Indeed, many psychrophilic or psychrotrophic bacteria inhabiting low-temperature
environments possess cold-adapted enzymes that exhibit high levels of activity even
at low temperatures (Siddiqui and Cavicchioli 2006; Marx et al. 2007).
Cold-adapted enzymes are generally known to exhibit higher levels of specific
activity at temperatures of 5–15 °C than the enzymes in microorganisms that
inhabit mesophilic regions. The specific activity of cold-adapted subtilisin at 10 °C,
for example, is roughly five times greater than that of ordinary subtilisin, while the
specific activity of cold-adapted amylase is around three times greater than that of
ordinary amylase (D’Amico et al. 2003). The reason for these higher levels of
specific activity stems from the fact that the rate of decrease in energy for reaction
activity by cold-adapted enzymes is greater than is the case for regular enzymes
(Smalås et al. 2000).
Additionally, cold-adapted enzymes exhibit lower heat stability than ordinary
enzymes, which means that their optimum temperature is also lower than that of
ordinary enzymes (10–20 °C lower for many enzymes). The use of cold-adapted
enzymes presents several advantages over regular enzymes. Perhaps the greatest of
these is that they exhibit high levels of activity even at low temperatures, which is
beneficial when they are operating on a substrate that is unstable with respect to
heat. Smaller quantities of enzymes can also be used than would be the case with
ordinary enzymes. In addition, while cold-adapted enzymes are unstable with
respect to heat, this actually presents an advantage in terms of being able to halt a
reaction easily through a short period of heat treatment. Since all activity in the
cold-adapted enzymes can be halted with brief heating, this allows for a decrease in
thermal changes in reaction products and their degradation through residual
activity.
To date, cold-adapted proteases, lipases, amylases, and cellulases have been
developed as cleaning supplements. These enzymes can be used to obtain strong
cleaning supplement effects even at low washing temperatures. Cold-adapted
enzymes are used in foods, including protease to tenderize meat, b-galactosidase to
break down lactose in milk, and pectinase for juice extraction and transparency.
These forms of food processing must be performed at low temperatures.
Cold-adapted enzymes are also suitable for uses in which enzymes must be completely deactivated with heating after a reaction, including the ligases and kinases
used in gene manipulation experiments.
Cold-adapted enzymes are likely to be used in various low-temperature bioprocesses in the future. This is likely to entail the use of various source organisms
from low-temperature environments such as deep-sea and polar waters.
11.4 Development of Biocatalysts from Microorganisms
401
number of physiological and biochemical changes. For this reason, they are believed
to possess enzymes with various properties related to low temperature adaptations.
Indeed, many psychrophilic or psychrotrophic bacteria inhabiting low-temperature
environments possess cold-adapted enzymes that exhibit high levels of activity even
at low temperatures (Siddiqui and Cavicchioli 2006; Marx et al. 2007).
Cold-adapted enzymes are generally known to exhibit higher levels of specific
activity at temperatures of 5–15 °C than the enzymes in microorganisms that
inhabit mesophilic regions. The specific activity of cold-adapted subtilisin at 10 °C,
for example, is roughly five times greater than that of ordinary subtilisin, while the
specific activity of cold-adapted amylase is around three times greater than that of
ordinary amylase (D’Amico et al. 2003). The reason for these higher levels of
specific activity stems from the fact that the rate of decrease in energy for reaction
activity by cold-adapted enzymes is greater than is the case for regular enzymes
(Smalås et al. 2000).
Additionally, cold-adapted enzymes exhibit lower heat stability than ordinary
enzymes, which means that their optimum temperature is also lower than that of
ordinary enzymes (10–20 °C lower for many enzymes). The use of cold-adapted
enzymes presents several advantages over regular enzymes. Perhaps the greatest of
these is that they exhibit high levels of activity even at low temperatures, which is
beneficial when they are operating on a substrate that is unstable with respect to
heat. Smaller quantities of enzymes can also be used than would be the case with
ordinary enzymes. In addition, while cold-adapted enzymes are unstable with
respect to heat, this actually presents an advantage in terms of being able to halt a
reaction easily through a short period of heat treatment. Since all activity in the
cold-adapted enzymes can be halted with brief heating, this allows for a decrease in
thermal changes in reaction products and their degradation through residual
activity.
To date, cold-adapted proteases, lipases, amylases, and cellulases have been
developed as cleaning supplements. These enzymes can be used to obtain strong
cleaning supplement effects even at low washing temperatures. Cold-adapted
enzymes are used in foods, including protease to tenderize meat, b-galactosidase to
break down lactose in milk, and pectinase for juice extraction and transparency.
These forms of food processing must be performed at low temperatures.
Cold-adapted enzymes are also suitable for uses in which enzymes must be completely deactivated with heating after a reaction, including the ligases and kinases
used in gene manipulation experiments.
Cold-adapted enzymes are likely to be used in various low-temperature bioprocesses in the future. This is likely to entail the use of various source organisms
from low-temperature environments such as deep-sea and polar waters.
11.4 Development of Biocatalysts from Microorganisms
401