The use of statistical methodology to optimize the
culture conditions and to improve enzyme production has
been a useful tool for biotechnology and has recently
received more attention. Some important parameters
should be considered for microorganism growth and secretion
of biotechnological products of industrial interest.
The RSM can be used to analyze the influence of different
parameters on enzyme production, to determine the
statistical significance level, and to examine the statistical
interactions among the factors involved in the process.
The “one-at-a-time” approach showed that four factors
(tannic acid, sodium nitrate, agitation rate and incubation
period) have the most influence on tannase production in
A. niger, and the use of the CCRD and RSM approaches
increased the enzymatic production 2-fold (from 9.8
U/mL to 19.7 U/mL) [23]. However, the tannase production
by Aspergillus sp. GM4 increased 2.66-fold using
the RSM under optimized conditions in submerged fermentation.
Tannase production in submerged fermentation
by Aspergillus sp. improves at high aeration rates
[20], as observed in studies with A. niger and Aspergillus
sp. GM4. The agitation rate shows an important effect on
the supply of nutrients, especially oxygen, for filamentous
fungi cultivation. Furthermore, good mixing, mass
and heat transfer require a threshold level of agitation.
However, high agitation rates can lead to high energy
dissipation rates and to high shear stress, which may result
in fragmentation and cell and mycelial network
damage [24]. Therefore, it is important to find the optimal
agitation rate for enzyme production without inducing
mycelium damage.