Lab-scale experiments
The preliminary experiments showed the relevance of
culture medium aeration and that the optimal inoculum
volume was 33 mL for 1 L medium (inoculum ratio 3.3%,
V/V).
To optimize fungal activity, the fungal consortium
can be accelerated with 24 hr aerated and agitated
pre-cultivation at ambient temperature. The pre-culture
medium consisted of whey or sugar cane molasses diluted
to achieve a lactose or a total sugar content of 5 g/L
respectively, or the dairy effluent itself and was also
inoculated at 3.3% (V/V) by the fungal consortium.
All tests were conducted in batch and perfectly shaken
media. Lab-scale experiments were carried out in 5 L
beakers, at a working volume of 4 L and at ambient temperature
and magnetically stirred. Aeration was performed
by means of an aquarium pump connected to a diffuser
allowing the production of fine air bubbles to ensure an
efficient oxygen transfer. Inoculation (3.3%, V/V) of the
fungal consortium accelerated (or not) was performed after
oxygen saturation of the culture medium. Considering the
real conditions, culture media were not sterilized.
For each culture medium, the following set of experiments
was carried out, which consisted of four different
runs: the culture medium inoculated with non-accelerated
fungi, with the fungal consortium accelerated on whey or
molasses diluted to achieve 5 g/L lactose or total sugar
content, and with the fungal consortium accelerated on
the same medium, as well as a blank experiment which
consisted of non-inoculated culture medium