Flocculation-flotation harvesting mechanism of Dunaliella salina: From nanoscale interpretation to industrial optimization

Besson, Alexandre; Formosa-Dague, Cécile; Guiraud, Pascal

doi:10.1016/j.watres.2019.02.043

Cited by 31 publications

(17 citation statements)

References 39 publications

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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.…”

mentioning

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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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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“…Flotation is often combined with flocculation to enable harvesting of concentrated flocs. This is an efficient harvesting method with reported harvesting yields of 93.6 % for S. obliquus by thermal flocculation and air flotation (Xue et al, 2019); or 80% harvesting of Dunaliella salina by combining NaOH-induced coagulation and DAF in the pre-industrial scale (Besson et al, 2019). Flotation has also been combined with bioflocculation either by inducing exopolysaccharides production in A. plantensis with more than 90% harvesting efficiency (Vergnes et al, 2019); or bioflocculant produced from Cobetia marina for the flocculation-flotation of C. vulgaris also with higher than 90% efficiency (Lei et al, 2015).…”

Section: Flotationmentioning

confidence: 99%

Current and novel approaches to downstream processing of microalgae: A review

Nitsos

Filali

Taidi

et al. 2020

Biotechnology Advances

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HAL is a multi-disciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L'archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

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“…Among microalgae, the most studied for the industrial production of carotenoids are the halophile microalga Dunaliella salina and the green alga Haematococcus pluvialis , which naturally produce high amounts of carotenoids [73]. Moreover, D. salina is a particularly versatile feedstock, and many researchers have focused on obtaining maximum carotenoid yields without impeding its growth [74,75,76]. In addition, D. salina has been successfully transformed via different approaches, such as microparticle bombardment [77] or via Agrobacterium tumefaciens [78], increasing the feasibility of its use for biotechnological applications.…”

Section: Enzymes From Microalgaementioning

confidence: 99%

Microalgal Enzymes with Biotechnological Applications

et al. 2019

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Enzymes are essential components of biological reactions and play important roles in the scaling and optimization of many industrial processes. Due to the growing commercial demand for new and more efficient enzymes to help further optimize these processes, many studies are now focusing their attention on more renewable and environmentally sustainable sources for the production of these enzymes. Microalgae are very promising from this perspective since they can be cultivated in photobioreactors, allowing the production of high biomass levels in a cost-efficient manner. This is reflected in the increased number of publications in this area, especially in the use of microalgae as a source of novel enzymes. In particular, various microalgal enzymes with different industrial applications (e.g., lipids and biofuel production, healthcare, and bioremediation) have been studied to date, and the modification of enzymatic sequences involved in lipid and carotenoid production has resulted in promising results. However, the entire biosynthetic pathways/systems leading to synthesis of potentially important bioactive compounds have in many cases yet to be fully characterized (e.g., for the synthesis of polyketides). Nonetheless, with recent advances in microalgal genomics and transcriptomic approaches, it is becoming easier to identify sequences encoding targeted enzymes, increasing the likelihood of the identification, heterologous expression, and characterization of these enzymes of interest. This review provides an overview of the state of the art in marine and freshwater microalgal enzymes with potential biotechnological applications and provides future perspectives for this field.

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Flocculation-flotation harvesting mechanism of Dunaliella salina: From nanoscale interpretation to industrial optimization

Cited by 31 publications

References 39 publications

Nanoscale Evidence Unravels Microalgae Flocculation Mechanism Induced by Chitosan

Nanoscale Evidence Unravels Microalgae Flocculation Mechanism Induced by Chitosan

Current and novel approaches to downstream processing of microalgae: A review

Microalgal Enzymes with Biotechnological Applications

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