RESUMO
Flocculation of microalgae with chitosan, polyacrylamide, Al2(SO4)3, NaOH and HNO3 was evaluated. Their flocculation efficiencies and optimal dosages were discussed. The effects of the flocculants on cells viability were also investigated and the cells were found to be intact during the flocculation process. Moreover, the effects of flocculants on the extractions were evaluated. Lipid content after flocculants treatments showed no significant differences. Carbohydrate content was lower but protein content was higher after NaOH treatment than those after other treatments. Furthermore, the five flocculated media maintained approximate growth yields to that of the fresh medium in microalgal cultivation, indicating the five flocculated media could be recycled, thereby reducing the cost of biodiesel production from microalgae. Finally, economic comparison of the flocculants was made and the cost of using HNO3, including flocculating cells and recycling medium, was found to be the lowest.
Assuntos
Biotecnologia/métodos , Floculação , Microalgas/fisiologia , Resinas Acrílicas/química , Resinas Acrílicas/economia , Resinas Acrílicas/farmacologia , Biocombustíveis , Biotecnologia/economia , Quitosana/química , Quitosana/economia , Quitosana/farmacologia , Custos e Análise de Custo , Meios de Cultura , Metabolismo dos Lipídeos/efeitos dos fármacos , Microalgas/química , Microalgas/efeitos dos fármacos , Ácido Nítrico/química , Ácido Nítrico/economia , Ácido Nítrico/farmacologia , Proteínas de Plantas/efeitos dos fármacos , Proteínas de Plantas/metabolismo , Reciclagem , Scenedesmus/efeitos dos fármacos , Scenedesmus/fisiologia , Hidróxido de Sódio/química , Hidróxido de Sódio/economia , Hidróxido de Sódio/farmacologiaRESUMO
A flocculation method was developed to harvest target microalgae with self-flocculating microalgae induced by decreasing pH to just below isoelectric point. The flocculation efficiencies of target microalgae were much higher than those flocculated only via pH decrease. The mechanism could be that negatively charged self-flocculating microalgal cells became positively charged during pH decrease, subsequently attracted negatively charged target microalgae cells to form flocs and settled down due to gravity. Microalgal biomass concentration and released polysaccharide (RPS) from target microalgae influenced flocculation efficiencies, while multivalent metal ions in growth medium could not. Furthermore, neutralizing pH and then supplementing nutrients allowed flocculated medium to be recycled for cultivation. Finally, Spearman's Rank Correlation Coefficients (Rs) between flocculation efficiency and key factors were also investigated. These results suggest that this method is effective, simple to operate and allows the reuse of flocculated medium, thereby contributing to the economic production from microalgae to biodiesel.
