From the results of the experimental design it was expected
that airflow rates above 6 l/(h g) bagasse would
increase xylanase production. Higher airflow rates were
therefore tested (10, 15 and 20 l/(h g)), but the xylanase
activity decreased, because with an additional air supply
it was not possible to maintain the level of medium moisture,
and after 48 h the moisture content decreased to 50%
(Fig. 2). This explains the variations in xylanase biosynthesis
even when the water content changed. The initial
moisture used in all the experiments (80%) had already
proven ideal for the xylanase activity of T. aurantiacus
[20]. In fact, an initial moisture above 80% decreased the
available interparticular spaces necessary for aeration of
the substrate, whereas a lower initial moisture decreases
the water activity, thus affecting cell growth and metabolite biosynthesis.