Photosynthetic carbon uptake induces autoflocculation of the marine microalga Nannochloropsis oculata

Tran, NAT; Seymour, JR; Siboni, N; Evenhuis, CR; Tamburic, B

Photosynthetic carbon uptake induces autoflocculation of the marine microalga Nannochloropsis oculata

Tran, NAT Seymour, JR

Siboni, N

Evenhuis, CR

Tamburic, B

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Publication Type:: Journal Article
Citation:: Algal Research, 2017, 26 pp. 302 - 311
Issue Date:: 2017-09-01

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Field	Value	Language
dc.contributor.author	Tran, NAT	en_US
dc.contributor.author	Seymour, JR https://orcid.org/0000-0002-3745-6541	en_US
dc.contributor.author	Siboni, N https://orcid.org/0000-0001-6082-0949	en_US
dc.contributor.author	Evenhuis, CR https://orcid.org/0000-0001-9903-7716	en_US
dc.contributor.author	Tamburic, B https://orcid.org/0000-0001-5720-9380	en_US
dc.date.issued	2017-09-01	en_US
dc.identifier.citation	Algal Research, 2017, 26 pp. 302 - 311	en_US
dc.identifier.issn	2211-9264	en_US
dc.identifier.uri	http://hdl.handle.net/10453/121982
dc.description.abstract	© 2017 Elsevier B.V. Microalgal biomass has been used to produce biofuels, aquaculture feed, high-value chemicals such as pigments and antioxidants, and even human food. This study addresses one of the key bottlenecks to the commercialisation of microalgal bioproducts: the high energy and environmental cost of harvesting microalgal cells out of suspension. An innovative and sustainable autoflocculation procedure was developed to pre-concentrate microalgal biomass for easier harvesting. Microalgal cell agglomeration by autoflocculation at high pH was induced for the first time, without the addition of a chemical flocculant, in the commercially-relevant microalga Nannochloropsis oculata. Photosynthetic inorganic carbon uptake, in the absence of carbon dioxide supply by mass transfer, was used to raise the culture pH. Autoflocculation started at pH 9.5 and reached a maximum flocculation efficiency of 90% at pH 10.4. Microalgal surface charge-neutralisation by calcium cations, and sweep flocculation by calcium carbonate and calcium phosphate precipitates were identified as the dominant flocculation mechanisms. This was also the first study to measure changes in bacterial community composition under autoflocculation. There was a clear shift from free-living bacteria in suspension to attached bacteria during autoflocculation, with Flavobacteriales becoming the dominant order of bacteria. This highlights the influential role of attached bacteria and bacteria-produced extracellular polymeric substances in microalgal flocculation. This study shows that regulating carbon dioxide supply is a promising green alternative to traditional microalgal flocculation processes as it alleviates the requirement for costly and harmful chemical flocculants and brings us closer to sustainable microalgal bioproducts.	en_US
dc.relation	http://purl.org/au-research/grants/arc/FT130100218
dc.relation.ispartof	Algal Research	en_US
dc.relation.isbasedon	10.1016/j.algal.2017.08.005	en_US
dc.title	Photosynthetic carbon uptake induces autoflocculation of the marine microalga Nannochloropsis oculata	en_US
dc.type	Journal Article
utslib.citation.volume	26	en_US
utslib.for	0605 Microbiology	en_US
utslib.for	0607 Plant Biology	en_US
utslib.for	0904 Chemical Engineering	en_US
utslib.for	1003 Industrial Biotechnology	en_US
pubs.embargo.period	Not known	en_US
pubs.organisational-group	/University of Technology Sydney
pubs.organisational-group	/University of Technology Sydney/Faculty of Science
pubs.organisational-group	/University of Technology Sydney/Strength - C3 - Climate Change Cluster
pubs.organisational-group	/University of Technology Sydney/Strength - ithree - Institute of Infection, Immunity and Innovation
utslib.copyright.status	closed_access
pubs.publication-status	Published	en_US
pubs.volume	26	en_US

Abstract:

© 2017 Elsevier B.V. Microalgal biomass has been used to produce biofuels, aquaculture feed, high-value chemicals such as pigments and antioxidants, and even human food. This study addresses one of the key bottlenecks to the commercialisation of microalgal bioproducts: the high energy and environmental cost of harvesting microalgal cells out of suspension. An innovative and sustainable autoflocculation procedure was developed to pre-concentrate microalgal biomass for easier harvesting. Microalgal cell agglomeration by autoflocculation at high pH was induced for the first time, without the addition of a chemical flocculant, in the commercially-relevant microalga Nannochloropsis oculata. Photosynthetic inorganic carbon uptake, in the absence of carbon dioxide supply by mass transfer, was used to raise the culture pH. Autoflocculation started at pH 9.5 and reached a maximum flocculation efficiency of 90% at pH 10.4. Microalgal surface charge-neutralisation by calcium cations, and sweep flocculation by calcium carbonate and calcium phosphate precipitates were identified as the dominant flocculation mechanisms. This was also the first study to measure changes in bacterial community composition under autoflocculation. There was a clear shift from free-living bacteria in suspension to attached bacteria during autoflocculation, with Flavobacteriales becoming the dominant order of bacteria. This highlights the influential role of attached bacteria and bacteria-produced extracellular polymeric substances in microalgal flocculation. This study shows that regulating carbon dioxide supply is a promising green alternative to traditional microalgal flocculation processes as it alleviates the requirement for costly and harmful chemical flocculants and brings us closer to sustainable microalgal bioproducts.

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http://hdl.handle.net/10453/121982