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See detailThe chlorophyll a fluorescence induction curve in the green microalga Haematococcus pluvialis: Further insight into the nature of the P-S-M fluctuation and its relationship with the "low-wave" phenomenon at steady-state
Fratamico, Anthony ULg; Tocquin, Pierre ULg; Franck, Fabrice ULg

in Photosynthesis Research (2016), 128(3), 271-285

Chlorophyll fluorescence is an information-rich signal which provides an access to the management of light absorbed by PSII. A good example of this is the succession of fast fluorescence fluctuations ... [more ▼]

Chlorophyll fluorescence is an information-rich signal which provides an access to the management of light absorbed by PSII. A good example of this is the succession of fast fluorescence fluctuations during light-induced photosynthetic induction after dark-adaptation. During this period, the fluorescence trace exhibits several inflexion points: O-J-I-P-S-M-T. Thereas the OJIP part of this kinetics has been the subject of many studies, the processes that underly the PSMT transient are less understood. Here, we report an analysis of the PSMT phase in the green microalga Haematococcus pluvialis in terms of electron acceptors and light use by photochemistry, fluorescence and non-photochemical quenching (NPQ). We identify additional sub-phases between P and S delimited by an inflexion point, that we name Q, found in the second time-scale. The P-Q phase expresses a transient photochemical quenching specifically due to alternative electron transport to oxygen. During the transition from Q to S, the NPQ increases and then relaxes during the S-M phase in about 1 min. It is suggested that this transient NPQ observed during induction is a high energy state quenching (qE) dependent the alternative electron transport to molecular oxygen. We further show that this NPQ is of the same nature than the NPQ, known as the low-wave phenomenon, which is transiently observed after a saturating light pulse given at steady-state. In both cases, the NPQ is oxygen-dependent. This NPQ is observed at external pH 6.0, but not at pH 7.5, which seems correlated with faster saturation of the PQ pool at pH 6.0. [less ▲]

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See detailLe démarrage de la photosynthèse chez une micro-algue
Fratamico, Anthony ULg

Speech/Talk (2014)

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See detailL'astaxanthine: de la biologie à l'industrie
Fratamico, Anthony ULg

Scientific conference (2014, May 06)

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See detailStudy of an undershoot in chlorophyll fluorescence signal after a saturating pulse in PAM measurements
Fratamico, Anthony ULg; Cardol, Pierre ULg; Tocquin, Pierre ULg et al

Conference (2014, April 14)

In 1989, Larcher and Neuner have reported the observation of a sudden reversible drop in modulated chlorophyll fluorescence measurements (PAM) immediately after a saturating pulse, and called it “low ... [more ▼]

In 1989, Larcher and Neuner have reported the observation of a sudden reversible drop in modulated chlorophyll fluorescence measurements (PAM) immediately after a saturating pulse, and called it “low-wave”. 25 years later, whereas some papers reported this phenomenon as a trivial detail, scarcely two works have investigated the origin of this particular signal, in which a link with a low CO2 availability seems clear. Our work on Haematococcus pluvialis, a freshwater green microalga, provides a new point of view on this fluorescence undershoot, caused by a rapidly established non-photochemical quenching. We have demonstrated that in the light-adapted state, a low-wave after a saturating flash can be considered as a consequence of an induction process engaged in response to the brief light increase under low CO2 conditions. The non-photochemical quenching during low-waves was found to be dependent on electron transport to oxygen during the preceding flash. Moreover, in conditions in which low-waves were observed in the light-adapted state, the fluorescence induction kinetics in the first minute of lighting after dark-adaptation presented also a reversible strong drop. Nevertheless, at the stationary state, oxygen production and photochemical yield of photosystem II were not affected. Providing a better understanding of the processes underlying low-waves, our work also draws attention on the effect of CO2 concentration on the onset of photosynthesis. [less ▲]

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See detailOptimization of an Haematococcus pluvialis medium by a Genetic Algorithm-based strategy
Fratamico, Anthony ULg; Tocquin, Pierre ULg; Franck, Fabrice ULg

Poster (2012, June 14)

The successful use of living organisms for the production of biomass or metabolites requires a careful control and optimization over growing conditions. However the range of interacting parameters makes ... [more ▼]

The successful use of living organisms for the production of biomass or metabolites requires a careful control and optimization over growing conditions. However the range of interacting parameters makes full optimization difficult and time-consuming. In this context, Genetic Algorithm-based (GA) methods emerge as promising strategies for optimization of biotechnological processes. However, the potential of GA in the microalgae field remains, today, poorly explored. As a proof-of-concept, we evaluated how GA could be applied for the optimization of a medium for high yield photoautotrophic growth of Haematoccocus pluvialis. [less ▲]

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See detailScreening for a low-cost Haematococcus pluvialis medium reveals an unexpected impact of a low N:P ratio on vegetative growth
Tocquin, Pierre ULg; Fratamico, Anthony ULg; Franck, Fabrice ULg

in Journal of Applied Phycology (2012), 24(3), 365-373

Haematococcus pluvialis is the current better source of natural astaxanthin, a high-value carotenoid. Traditionally, the production process of astaxanthin by this algae is achieved by a two-stage system ... [more ▼]

Haematococcus pluvialis is the current better source of natural astaxanthin, a high-value carotenoid. Traditionally, the production process of astaxanthin by this algae is achieved by a two-stage system: during the first stage, vegetative “green” cells are produced and then converted, in the second stage, into cysts that accumulate astaxanthin. In this work, a medium screening strategy based on the mixing of a 3-component hydroponic fertilizer was applied to identify a new formulation optimized for the vegetative stage. A maximal and high cell density of 2 x 106 cells mL−1 was obtained in a medium containing a high level of phosphate relative to nitrate, resulting in a N:P ratio much lower than commonly used media for H. pluvialis. In this medium, cells remained at the vegetative and motile stage during a prolonged period of time. Both high cell density culture and motile stage persistence was proved to be related to the N:P feature of this medium. We conclude that the macrozoid stage of H. pluvialis is favored under high-P and low-N supply and that low-cost hydroponic fertilizers can be successfully used for achieving high density cultures of vegetative cells of H. pluvialis. [less ▲]

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See detailAmélioration des conditions de culture d'Haematococcus pluvialis, producteur naturel d'astaxanthine. Importance du rapport N:P sur le contrôle du cycle de développement
Fratamico, Anthony ULg

Master's dissertation (2010)

Haematococcus pluvialis is a Chlorophyta industrially used for its ability to synthetise and to accumulate a high-value molecule: the astaxanthin (3,3'-dihydroxy-beta,beta'-carotene-4,4'-dione), a ... [more ▼]

Haematococcus pluvialis is a Chlorophyta industrially used for its ability to synthetise and to accumulate a high-value molecule: the astaxanthin (3,3'-dihydroxy-beta,beta'-carotene-4,4'-dione), a carotenoid of the xanthophyll familly. This pigment is used, i.e., as dye in food but, because of its antioxydant properties, applications in human health are also promising. The accumulation of this pigment occurs during a specific stage in the complex life cycle of this micro-algae. Thus, the understanding and the control of this cycle is a important key for a good production. In addition, the culture of H. pluvialis in countries where climate is not favourable to outdoor systems requires the conception of indoor photobioreactors. We have searched to improve the astaxanthin production by H. pluvialis in an indoor photobioreactor context, much adapted to our country. For this, we have tried to redefine optimal growth conditions by an original approach. The search for an ideal culture medium was made by a "blind" screening in batch mode. Then, we have tested the efficacy of our formulation in a semi-continuous culture system. The impact of the macro-elements on the H. pluvialis life cycle and on the expression levels of genes implicated in the astaxanthin biosynthesis were also studied. Our results allowed us to build up a photobioreactor prototype with an original design which may be a first step for the elaboration of a highly effective system for astaxanthin production by H. pluvialis. [less ▲]

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