PROTEASES FROM CELL CULTURE OF Bromelia hemisphaerica ...

FSB1 – 2004
Food Science and Biotechnology in Developing Countries
It is important to make a mention that experiments were called as “repression experiments”
however, it is very clear that in this study, glucose has a double role on invertase expression,
because at lowest initial concentrations it acts like activator of biomass production and it has a
direct effect on invertase production. In contrast, at higher than 12.5 g/L of glucose, this
molecule acts as repressor of the invertase production.
To evaluate the degree of modification on invertase production by two molecules used, it was
decided to stablish a induction or repression ratio. Both ratios were calculated dividing the
maximal invertase level at each experiment by the basal activity obtained in experiments with
glucose as sole carbon source at 30 g/L.
Figure 3 shows the results of induction and repression ratios for the invertase in different initial
concentrations of inductor and repressor enzymatic.
Repretion Ratio
250,0
200,0
150,0
100,0
50,0
0,0
R.R. I.R.
0 6.25 12.5 25 50 100
Initial Concentration (g/L)
Figure 3. Induction ratio at several sucrose concentrations (white rhombus)
and repression ratio at several glucose concentrarions and 25 g/L of sucrose
(black squares).
Use of glucose in culture medium stimulated significantly the invertase production; however, this
increasing capacity of glucose in enzyme activity is reverted at higher initial concentration of
50g/L. Cultures with inducer and glucose at initial concentration lower than 50 g/L favored the
invertase expression in comparison with those results obtained with sole inducer. This behavior
has been described previously by Aguilar et al (2001) using as study model the tannase
enzyme produced by the same fungus.
The best initial concentration of enzymatic inducer was 50g/L, obtain maximum activity at 60
hours with 2170.8U/L*min and the best initial concentration of repressor was at 6.25g/L with an
15
10
5
0
Induction Ratio