Biomedical Engineering Reference
In-Depth Information
These results indicate that there is a statistically significant relationship between the variables
at the 95% confidence level as well as an excellent adequacy of the quadratic models to the
experimental data.
The response surface obtained from the empirical model (1) is depicted in Figure 3.
Optimal residual amylase activity (95 %) was at pH 5.8 (coded value of 0.23) and 46.4ºC
(coded value of 0.09), with visible decrease toward low or high values of both variables
(Figure 3).
Table 5. Significance analysis of the model (1) obtained for remaining amylase activity
after treatment of pH and temperature
SS
fd
QM
Model
7869.7
4
1967.4
Error
121.8
8
15.2
Exp. error
59.4
4
14.8
Lack of fitting
62.5
4
15.6
Total
7991.5
12
1982.6
QME/QMEe
= 1.03
F
8
4
(α = 0.05) = 6.04
QMLF/QMEe = 1.05
F
4
4
(α = 0.05)
=
6.39
r
2
= 0.985 adj
r
2
= 0.977
SS: Sum of Squares; df: degrees of freedom; QM: Quadratic Means; E: total error; Ee: Experimental error;
LF: Lack of Fitting.
120
90
60
120
90
60
30
30
1,3
1,3
0
0
-1,3
-1,3
Figure 3. Response surface showing the influence of pH and temperature on the total amylolytic
activity (
TAA
) produced by
A. oryzae
FQB-01 in BW medium.
T
and
pH
are in coded values.
On the other hand, when amylase samples were adjusted at optimum pH value of 5.8 and
incubated at 40, 50, 60 and 70ºC in absence of substrate (starch), the enzyme retained
approximately 85% of its initial activity after 1 h of incubation at 40 and 50ºC (left part of
Figure 4). However, at 60 and 70ºC the initial amylase activity was completely lost after 50
and 30 min of incubation, respectively.
