Bicarbonate Concentration Induces Production of Exopolysaccharides by <i>Arthrospira platensis</i> That Mediate Bioflocculation and Enhance Flotation Harvesting Efficiency

Vergnes, Jean-Baptiste; Gernigon, Vincent; Guiraud, Pascal; Formosa-Dague, Cécile

doi:10.1021/acssuschemeng.9b01591

Cited by 35 publications

(17 citation statements)

References 42 publications

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“…The inorganic carbon source most commonly used is CO 2 (0.05-10% v/v) combined with air and used to control pH on demand . NaHCO 3 was found to positively influence EPS production in Arthropira platensis while at the same time it also promoted bioflocculation with almost 90% of harvest efficiency [66]. Some authors have evaluated the effect of using organic carbon sources.…”

Section: Culture Mediummentioning

confidence: 99%

Exopolysaccharides from Cyanobacteria: Strategies for Bioprocess Development

et al. 2020

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Cyanobacteria have the potential to become an industrially sustainable source of functional biopolymers. Their exopolysaccharides (EPS) harbor chemical complexity, which predicts bioactive potential. Although some are reported to excrete conspicuous amounts of polysaccharides, others are still to be discovered. The production of this strain-specific trait can promote carbon neutrality while its intrinsic location can potentially reduce downstream processing costs. To develop an EPS cyanobacterial bioprocess (Cyano-EPS) three steps were explored: the selection of the cyanobacterial host; optimization of production parameters; downstream processing. Studying the production parameters allow us to understand and optimize their response in terms of growth and EPS production though many times it was found divergent. Although the extraction of EPS can be achieved with a certain degree of simplicity, the purification and isolation steps demand experience. In this review, we gathered relevant research on EPS with a focus on bioprocess development. Challenges and strategies to overcome possible drawbacks are highlighted.

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Section: Culture Mediummentioning

confidence: 99%

Exopolysaccharides from Cyanobacteria: Strategies for Bioprocess Development

et al. 2020

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“…Our team recently used AFM to understand the flocculation mechanism involved in the cases of three different microalgae species, demonstrating the interest of using this technology to answer such questions. [34][35][36] Thanks to AFM force spectroscopy experiments, we show for the first time that at pH 6 below its pKa, chitosan interacts with C. vulgaris cell wall through non-electrostatic interactions, i. e. through specific interactions between chitosan and polymers at the surface of cells that are being unfolded upon retraction. These observations were confirmed by comparing the data obtained with cationically modified cellulose nanocrystals (CNCs), for which the flocculation mechanism, relying on an electrostatic patch mechanisms, has been suggested in a previous study from our team on C. vulgaris.…”

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confidence: 93%

Nanoscale Evidence Unravels Microalgae Flocculation Mechanism Induced by Chitosan

Demir

Blockx

Dague

et al. 2020

ACS Appl. Bio Mater.

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In light of climate change, there is a growing interest for sustainable energy. Microalgae are a promising resource for biofuel production, although their industrial use is limited by the lack of effective harvesting techniques. Flocculation consists in the aggregation and adhesion of cells into flocs that can be more easily removed from water than individual cells. Although it is an efficient harvesting technique, contamination is a major issue as chemical flocculants are often used. An alternative is to use natural biopolymers flocculants, such as chitosan. Chitosan is a bio-based nontoxic polymer, which has been effectively used to harvest Chlorella vulgaris cells at pH lower than its pKa (6.5). While the flocculation mechanism reported relied on electrostatic interactions between chitosan and the negative cell surface, no molecular evidence has yet confirmed this mechanism. In this study, we performed force spectroscopy AFM experiments to probe the interactions between C. vulgaris cells and chitosan at the molecular scale to decipher its flocculation mechanism. Our results showed that at pH 6, chitosan interacts with C. vulgaris cell wall through biological interactions, rather than electrostatic interactions. These observations were confirmed by comparing the data with cationically modified cellulose nanocrystals, for which the flocculation mechanism, relying on an electrostatic patch mechanism, has already been described for C. vulgaris. Further AFM experiments also showed that a different mechanism was at play at higher pH, based on chitosan precipitation. Thus this AFM-based approach highlights the complexity of chitosan-induced flocculation mechanisms for C. vulgaris.

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“…Using this mode, Vergnes and co-workers could show that the EPS produced by A. platensis formed a soft, adhesive gel in the medium surrounding the cells. Thanks to these information, the authors could conclude on the role of these EPS on cell flocculation and thus on the possibility to harvest them [31].…”

Section: Imaging Of Microalgae Cells With Nanoscale Resolutionmentioning

confidence: 99%