Affects the Activity and Stability of Enzymes?
processing levels usually dictate some variation in physical
conditions under which the enzyme products must function. In
order to utilize enzymes to their optimal potential in catalytic
ability, we must be familiar with the basic principles that
can affect the activity and stability of these enzymes. Enzymes,
being biological compounds and being comprised of a high percentage
of protein, are subject to many environmental effects. Although
the following principles hold true for most biological enzymes
produced for commercial agricultural use:
The pH of the environment has a profound affect on
enzyme activity and stability. Activity optimal for pH's of
various enzymes vary; however, the optimal pH's for the
biological catalysts produced by most commercial strains
of microorganisms lies between pH 4.0 and 7.5. This range is
from moderately acidic to mildly alkaline in nature. These
are the pH levels normally encountered. Figure 1, indicates
a difference in activity levels that various enzymes exhibit
at varying pH levels.
Another major affect of enzyme activity and stability is temperature.
Since enzymes are biochemical catalysts, made up at least partially
of protein, they are sensitive in varying degrees to heat.
Raising temperatures of the environment generally
multiplies the degree of activity by the enzyme. Once an optimum
temperature has been reached, however, even higher temperatures
cause rapid degradation of the enzyme with concurrent and
irreversible loss in activity. Optimal temperatures generally range
from 98 °F to 140 °F (37
°C to 60 °C) for
most hydrolytic enzymes. High temperatures (over 150 °F,
generally have detrimental effects on the
enzymes. However, there is broad variation in resistance and sensitivity to heat
among the enzymes' types. Bacterial enzymes such as those
from Bacillus subtilis
are less sensitive to heat than are the fungal enzymes of
Some amylase preparations prepared by the fermentation of Bacillus
species can withstand even boiling for short periods and
have optimal activities in the 158
°F - 176 °F
°C - 80 °C)
range. Our laboratory has determined that approximately 85% of the
activity from Bacillus
subtilis/licheniformis alpha-amylase survives
high heat. A. oryzae amylases,
however, showed a greater than 90% loss activity in high heat. When
the enzyme-bearing, dried fermentation products of these two
microorganisms are kept dry, they are much more resistant to environmental
temperature stress than if they are moistened. In fact, very
few stability problems are encountered with most enzymes
in typical situations.
Basic Knowledge of Enzymes Applied
Making use of general knowledge about enzymes including how they
act, under what conditions they perform, and how to preserve their
activity is important in applying the technology of enzymes to organic
Helpful References on Enzymes:
Aunstrup, K. 1979. In Enzyme Technology, L.B. Wingard, Jr., E. Katchalek-Katzir,
L. Goldstein (ed). Academic Press, Inc., New York.
Boyer, P.D. (ed). 1971. The enzymes, 3rd, ed. Vol. 5. Academic Press,
Inc., New York.
Fogarty, W. M. 1974. Enzyme technology - projects and developments.
In Projects and prospects in industrial fermentation: proceedings
of meeting held in Holly Royde. A. J. Powell and J. D. Bu'Lock (ed).
U. of Manchester. Manchester, England.
Godfrey, T. and J. Reichelt (eds). 1983. Industrial enzymology:
the application of
enzymes in industry. Nature Press. New York.
Kulp, K. 1975. Carbohydrases and other enzymes.