AMYLASE PRODUCTION BY ASPERGILLUS ORYZAE IN SUBMERGED AND SOLID STATE FERMENTATIONS - Biochemical Engineering - page 198

The three-dimensional response surface (Figure 6) shows that the maximum TAA (197
EU/gds) was obtained at pH 5.9 (coded value of 0.55) and 32.5ºC (coded value of 0.24).
Thus, A. oryzae exhibited its best performance for enzyme production in the mesophilic range
(Figure 6), as it was reported before for A. oryzae NRRL 6270, which produce the highest α-
amylase level in the range from 25 to 30ºC (Francis et al., 2003).
High temperature values may lead to enzymatic inactivation (Mazutti et al., 2006) or
suppression of cell viability and death (Pandey et al., 2001; Francis et al., 2002), meanwhile
low temperature values may reduce the metabolism of the microorganism (Mazutti et al.,
2006) and consequently, the enzyme production.

Table 7. Significance analysis of the model (2) obtained for TAA production under
different initial pH and temperature conditions

SS fd QM

Model 20511.9 4 5128.0

Error 1301.2 8 162.6

Exp. error 252.8 4 63.2

Lack of fitting 1048.4 4 262.1

Total 21813.1 12 1817.7

QME/QMEe = 2.57 F 8 4 (α = 0.05) = 6.04
QMLF/QMEe = 4.15 F 4 4 (α = 0.05) = 6.39
r 2 = 0.940 adj r 2 = 0.911
SS: Sum of Squares; df: degrees of freedom; QM: Quadratic Means; E: total error; Ee: Experimental error;
LF: Lack of Fitting.

In this study, it was verified that A. oryzae FQB-01 has a preference to pH around 6.0 for
TAA production. However, its production capacity decreased for pH levels higher and lower
than the optimum pH probably as a consequence of a reduction in the metabolic activity of
the amylase-producing strain at these pH values (Ellaiah et al., 2002).

Table 8. Results of the experimental design showing both the experimental and the
calculated values of TAA levels in function of the total sugars (TS in mg/gds), moisture
content (M in %) and inoculum size (IS) as log (number of spores/gds) and significance
analysis of the model coefficients

Natural values TAA (EU/gds)

Observed
response

M IS TS Predicted value

80 8.0 60.0 470.3 461.0

80 8.0 20.0 347.1 328.1

80 5.0 60.0 400.2 373.1

80 5.0 20.0 218.6 240.2

63 8.0 60.0 342.6 333.2

63 8.0 20.0 228.6 265.7

63 5.0 60.0 243.4 245.3

63 5.0 20.0 183.3 177.8

59 6.5 40.0 189.8 173.0