Harvesting Microalgae With Chitosan

Abstract

We have studied the use of chitosan as a non‐toxic flocculant to concentrate freshwater cultures of microalgae; these are part of a biological tertiary treatment system of urban wastewaters intended to produce biomasses for animal feeding. The sedimentation rate measured at increasing concentrations of chitosan showed that, under appropriate conditions (pH, stirring, etc.), a recovery of 95% or more of the algae was obtained at chitosan concentrations lower than 40 mg/liter. This result was obtained with temperatures ranging from 5 to 25°C and with an algal biomass concentration of 100–150 mg dry weight/liter. Results are also presented for biomass concentrations up to 1 g dry weight/liter. On the basis of these results, economic feasibility is examined by comparison with synthetic polyelectrolytes which appear to be the only other flocculants leading to a similar efficiency. Extension of the process to marine algae is also presented.

Nanomaterial processing strategies in functional hybrid materials for wastewater treatment using algal biomass

“…Chitosan has desirable properties for bioprocesses, in particular because of its biodegradability and lack of toxicity. It is a natural based polymer generated by the deacetylation of chitin, which is a natural component of the exoskeletons of crustaceans . Chlorella vulgaris cells have negative charge on their cell walls with a zeta potential value of approximately −30 mV in neutral water, and this results in an electrostatic attraction to positively charged protonated amino groups of chitosan which are generated at neutral environmental (zeta potential value of around +20 mV) .…”

“…It is a natural based polymer generated by the deacetylation of chitin, which is a natural component of the exoskeletons of crustaceans. 19 Chlorella vulgaris cells have negative charge on their cell walls with a zeta potential value of approximately −30 mV in neutral water, 20 and this results in an electrostatic attraction to positively charged protonated amino groups of chitosan which are generated at neutral environmental (zeta potential value of around +20 mV). 21,22 Microalgal composites with the above electrospun nanofibers resulted in efficient nitrate removal from liquid effluents (up to 87% of the initial value), which arises from the dual action of biological nitrate reduction by the microalgal cells and electrostatic binding of extra nitrate ions on the chitosan nanofibers.…”

Chitosan-graft-polydiallyldimethyl ammonium chloride for microalgae harvesting from wastewater

“…To achieve sustainability in microalgae harvesting, organic coagulants must be tested and utilized. Organic coagulants such as cationic starch, chitosan, and guar gum have been to a certain extent researched for microalgae harvesting [9,[11][12][13]. Organic coagulants are naturally available, inexpensive, and can provide a source of carbon for downstream processes such as in fermentation or anaerobic digestion of the harvested biomass.…”

Mechanism of Algal Aggregation by Bacillus sp. Strain RP1137

“…Uduman et al provide an excellent review of different algal harvest methods, including the advantages and disadvantages of each (6). Bio-aggregation uses biological agents such as extracellular polymeric substances, chitosan, or whole cells to form easily harvestable aggregates (7)(8)(9)(10)(11). Several algaaggregating bacterial strains are known and have been proposed for use in harvesting algae (12)(13)(14)(15)(16)(17).…”