Ionic effects on microalgae harvest via microalgae-fungi co-pelletization

Carlos Zamalloa, Sarman Oktovianus Gultom, Aravindan Rajendran, Bo Hu

Research output: Contribution to journalArticlepeer-review

11 Scopus citations


Microalgae harvesting is a difficult and costly unit operation, hampering commercial microalgae based processes. Various innovative approaches have been under research investigations. Algae harvesting using microalgae/fungi co-pelletization where microalgae cells are attracted to filamentous fungus and form co-pellets during their co-culture has been proved to be an innovative approach that might be both cost effective and sustainable. Yet, the mechanism behind the co-pelletization based algae harvesting is still not known. Understanding its mechanism will significantly facilitate future developments to decrease the processing cost for generating biofuel and other microalgae based bio-products. Considering that the ionic conditions greatly affect the flocculation performance of microalgae cells, studies were conducted to compare the co-pelletization performance at different pH values and ionic strengths in order to evaluate the surface charge changes at the different conditions tested. Zeta-potential measurements indicated that (1) both microalgae and fungi have low negative zeta-potentials regardless of the pH of the bulk solution (<−10 mV) (2) fungi can have a positive electric charge at low pH (pH=3). The results suggest that it might be possible that the degree of repulsion and dispersion between these organisms is low at certain conditions, for instance, at higher concentrations of Ca2+ (>0.1 g/L) the surface charge of fungal and microalgae cells were less negative (>−5 mV for fungal hyphae and >−12 mV for microalgae) at higher concentrations of magnesium (0.5 g/L), which might have facilitated the attraction between them.

Original languageEnglish (US)
Pages (from-to)145-155
Number of pages11
JournalBiocatalysis and Agricultural Biotechnology
StatePublished - Jan 1 2017


  • Algae harvest
  • Aspergillus niger
  • Biomass recovery
  • Chlorella vulgaris
  • Co-pelletization


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