Plant-based biopolymers: emerging bio-flocculants for microalgal biomass recovery.

The production of microalgal biomass and
its derived products on a large-scale requires the
development of sustainable and cost-effective harvesting
technologies. Biomass recovery is the primary
step in the downstream processing of microalgae and it
is a costly operation because microalgal cultures are
stable hydrophilic colloidal suspensions. Bio-flocculation
has been proposed as a low-cost technology that
can be employed to dewater microalgal cultures thus
making secondary harvesting methods like filtration
and centrifugation less energy-intensive. This review
provides an overview of increasing applications of
plant-based biopolymers in microalgal biomass harvesting
on laboratory and pilot-scale culture volumes.
The structure, preparation, and flocculation activity of
natural and chemically cationized plant biopolymers
are presented. Recent studies demonstrating microalgal
biomass recovery have been summarized discussing
the advantages and limitations of plant-based
biopolymers as emerging bio-flocculants. Future perspectives
on biopolymers with special attention to
studies reported on nutrient medium recycling, environmental
impact assessment and techno-economic
analysis of plant-based bio-flocculants facilitated bioflocculation
have been discussed.