The morphological features of the fungus–algae complex after
breakup were observed using microscopes under 40 and
100 magnification (Fig. 5A–D). The micrographs showed that almost
all microalgal cells were entrapped by filamentous hyphae of
A. oryzae The exact mechanism for fungus–algae pellet formation is
not clearly, and may vary from species to species and strain to
strain [28]. Continuous agitation was considered as one of the
key reasons for fungus–algae complex formation [9–11,28]. Our
results showed fungus–algae pellets did not form without agitation
(data not shown). Fujia et al [11] reported that shearing stress
created by hydraulic movements may contribute significantly to
pellet formation. Surface properties of fungi were believed to play
another major role [36]. It was found that the hydrophobic
proteins on the mycelial surface of some filamentous might be
beneficial to fungus–algae pellet formation because these hydrophobic
proteins could attach to solid surface and assist fungisolid
aggregation/pelletization [36]. The surface charges on
microalgae and filamentous fungus might be another reason for
fungus–algae pellet formation. Subramanian reported that a new
isolated pellet-forming fungal strain Penicillium strain BS30 carried
positive charges [10] while microalgae were typically negatively
charged [7], which could cause aggregation of positively charged
microalgae and negatively charged fungi. However, surface charge
was considered to vary with pH variation of medium, charges after
biodegradation as well as microbial extracellular-polymeric substances
[37], which might have a reverse effect on pellet formation
and be strain-specific [28]. In summary, the detailed mechanism of
pelletized fungus–algae complex in this study is not very clear up
to now and deserves further investigation.
The morphological features of the fungus–algae complex afterbreakup were observed using microscopes under 40 and100 magnification (Fig. 5A–D). The micrographs showed that almostall microalgal cells were entrapped by filamentous hyphae ofA. oryzae The exact mechanism for fungus–algae pellet formation isnot clearly, and may vary from species to species and strain tostrain [28]. Continuous agitation was considered as one of thekey reasons for fungus–algae complex formation [9–11,28]. Ourresults showed fungus–algae pellets did not form without agitation(data not shown). Fujia et al [11] reported that shearing stresscreated by hydraulic movements may contribute significantly topellet formation. Surface properties of fungi were believed to playanother major role [36]. It was found that the hydrophobicproteins on the mycelial surface of some filamentous might bebeneficial to fungus–algae pellet formation because these hydrophobicproteins could attach to solid surface and assist fungisolidaggregation/pelletization [36]. The surface charges onmicroalgae and filamentous fungus might be another reason forfungus–algae pellet formation. Subramanian reported that a newisolated pellet-forming fungal strain Penicillium strain BS30 carriedpositive charges [10] while microalgae were typically negativelycharged [7], which could cause aggregation of positively chargedmicroalgae and negatively charged fungi. However, surface chargewas considered to vary with pH variation of medium, charges after
biodegradation as well as microbial extracellular-polymeric substances
[37], which might have a reverse effect on pellet formation
and be strain-specific [28]. In summary, the detailed mechanism of
pelletized fungus–algae complex in this study is not very clear up
to now and deserves further investigation.
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