Biomedical Engineering Reference
In-Depth Information
Table 4. Comparison of the observed and the predicted responses (remaining amylase
activity) after pH and temperature treatment and significance analysis of the model
coefficients
Natural values
Remaining TAA (%)
T
pH
Observed response
Predicted value
60
7.0
58.94
59.04
60
4.0
39.14
37.92
30
7.0
43.16
48.49
30
4.0
28.04
27.37
64
5.5
53.85
55.03
26
5.5
45.06
41.67
45
7.4
75.65
71.66
45
3.6
43.12
44.90
45
5.5
89.63
94.44
45
5.5
92.34
94.44
45
5.5
100.00
94.44
45
5.5
94.00
94.44
45
5.5
95.36
94.44
Significance analysis of coefficients
Factor
Coefficient
t
-value
Constant
94.4
55.34*
T
5.3
3.67*
pH
10.6
7.36*
T·pH
1.2
0.61
T
2
-28.7
16.92*
pH
2
-22.5
13.28*
*
Significant at t (α < 0.05; υ = 4) > 2.78.
Effect of pH and Temperature on the Stability of Enzymes
Samples of amylase previously produced in BW medium supplemented with 40 g of
starch/L, were used to test the effect of temperature and pH on the enzyme activity using a
second order orthogonal design. Table 4 summarizes the responses for each individual
experiment along with the predicted responses.
The model equation fitted by regression analysis is given by:
TAA
(%) = 94.4 + 5.3
T
+ 10.6
pH
- 28.7
T
2
- 22.5
pH
2
(1)
where
TAA
is the remaining total amylolytic activity and
T
is the temperature. The model
terms
T
,
pH
,
T
2
and
pH
2
were found to be significant according to the Student
t
-test (α <
0.05), meanwhile the interaction term between
T
and
pH
variables (
T·pH
) was found to be
non significant (Table 4).
The equation (1) was significant in Fisher`s
F
-tests (
α
< 0.05) applied to both quotients
total error/experimental error and lack of fitting/experimental error (Table 5). In addition, the
value of the adjusted determination coefficient (adj.
r
2
) was calculated to be 0.977 (Table 5).
