good growth in aerobic or agitation culture, but color removal
was obtained with a high efficiency in anoxic or anaerobic
culture.
Azo linkages are easily reduced under anaerobic conditions
[8,9], yielding colorless aromatic amines which, with a few
exceptions [10], are not mineralized anaerobically, but are
readily degraded aerobically. Therefore, a combination of anaerobic
and aerobic conditions is proposed for azo compounds’
mineralization [11,12].
Microbial decolorization of reactive azo dyes has been
reached by sequential anaerobiceaerobic system [13]. Integration
of anaerobic and aerobic conditions in a single bioreactor
has been developed with a methanogenic granular sludge exposed
to oxygen [14,15]. Also a simultaneous anaerobic and
aerobic degradation for an azo dye by two different cultures
immobilized in calcium alginate beads was described [16].
In this case, one bacterial strain caused the reduction of the
azo dye in the anaerobic zone leading to the formation of aromatic
amines, and the second strain could mineralize the
amines in the aerobic zone.