Bacteria or fungi can also induce bioflocculation of
microalgae. Some fungi, for instance, have positively
charged hyphae that can interact with the negatively
charged microalgal cell surface and cause flocculation
[49,50]. Specific consortia of bacteria can also induce flocculation
of microalgae [51,52]. These flocculating fungi or
bacteria can be cultivated separately or in combination
with the microalgae. Cultivating bacteria or fungi in combination
with microalgae requires a carbon source in the
medium. In wastewater, a carbon source is usually present
and this allows cocultivation of microalgae and bacteria.
This results in a culture of mixed algal–bacterial flocs that
can be easily harvested [53,54]. The use of bacteria or fungi
as a flocculating agent avoids chemical contamination of
the biomass but results in microbiological contamination,
which may also interfere with food or feed applications of
the microalgal biomass.