d(GC) - Association of Biotechnology and Pharmacy

Current Trends in Biotechnology and Pharmacy
Vol. 6 (2) 241-254 April 2012, ISSN 0973-8916 (Print), 2230-7303 (Online)
of the mutual interactions between the test
variables. The F value and the corresponding P
values, along with the coefficient estimate, are
given in Table 2. The smaller the magnitude of
the P, the more significant is the corresponding
coefficient. Values of P less than 0.050 indicate
the model terms to be significant. The coefficient
estimates and the corresponding P values
suggests that, among the test variables used in
the study, B, C, A 2 , B 2 , AB, AC and BC (where A
= glucose, B = yeast extract, C = MgSO 4 ) are
significant model terms. B, A 2 , B 2 and AB (P <
0.0001) have the largest effect on GSH
production. Other intearctions were found to be
insignificant.
The corresponding second-order response
model for Eq. (7) that was found after analysis
for the regression was:
GSH (mg/L) = 139.13 – (0.70 x glucose) +
(13.38 x yeast extract) – (2.29 x magnesium
sulphate) – (24.94 x glucose 2 ) – (27.50 x yeast
extract 2 ) + (0.71 x magnesium sulphate 2 ) + (11.40
x glucose x yeast extract) + (5.47 x glucose x
249
magnesium sulphate) – (5.12 x yeast extract x
magnesium sulphate) (7)
The fit of the model was also expressed by
the coefficient of regression (r 2 ), which was found
to be 0.996, indicating that 99.6 % of the
confidence level of the model to predict the
response (GSH yield). The “Pred R-Squared” of
0.975 is in reasonable agreement with the “Adj
R-Squared” of 0.992. “Adeq Precision” measures
the signal to noise ratio. A ratio greater than 4 is
desirable. Here, the ratio of 47.095 indicates an
adequate signal. The special features of the RSM
tool, “contour plot generation” and “point
prediction” were also studied to find optimum
value of the combination of the three media
constitutes for the maximum production of GSH.
These predicted values were experimentally
verified. Table 3 documents the predicted and
experimental yields of GSH by various media
combination. It was observed that medium
containing (%), glucose 5.67, yeast extract, 7.13
and magnesium sulphate, 0.66 yielded maximum
(148.45 mg/L) GSH.
Table 2. Analysis of variance (ANOVA) for the experimental results of the central
composite design (Quadratic Model)
Factor a Estimate Sum of Standard DF b F value p
Coefficient squares Error
Intercept 139.13 61.28 1.25 1 270.75 < 0.0001
A -0.70 6.71 0.82 1 0.73 0.4159
B 13.38 2445.59 0.82 1 264.87 < 0.0001
C -2.29 71.52 0.82 1 7.75 0.0213
A 2 -24.94 8953.57 0.80 1 969.70 < 0.0001
B 2 -27.50 10888.97 0.80 1 1179.31 < 0.0001
C 2 0.71 7.18 0.80 1 0.78 0.4009
AB 11.40 1039.22 1.07 1 112.55 < 0.0001
AC 5.47 238.93 1.07 1 25.88 0.0007
BC -5.12 209.51 1.07 1 22.69 0.0010
a A = glucose, B = yeast extract, C = MgSO4
b Degree of freedom, p < 0.05 (models are significant), R 2 = 0.99
Enhanced Production of Glutathione