A method to assess algicidal activity of microalgal extracts coupling microalgae produced in stirred closed photobioreactor operating in continuous with pulse amplitude modulated (PAM) fluorometry

Eva Menguy,Vincent Dumontet,Noémie Coulombier,Vincent Meriot,Loïc Le Déan,Vanille Barthelemy,Thierry Jauffrais

doi:10.1016/j.mex.2020.101037

Abstract

We describe in the present study a quick and reliable method based on chlorophyll a fluorescence to assess putative algicidal effect of different microalgal extracts. We couple microalgal production under chemostat cultivation mode to continuously produce a given microalgae species (e.g. Dunaliella salina in this study) at a stable physiological state to ease comparison between extracts tested; with a non-destructive method based on chlorophyll a fluorescence. Pulse amplitude modulated (PAM) fluorometry was used to assess over time the effect of different microalgal crude extracts on the efficiency of the photosystem II (PSII) of a tested microalgae (Dunaliella salina).• Microalgal production at stationary phase in stirred closed photobioreactor (PBR) operating in continuous have stable photophysiological parameters, which is a prerequisite to compare the impact of different algicidal compounds.• The combination of both methods, allows to quickly assess the algicidal effect of diverse microalgal (crude) extracts on the PSII efficiency of a tested microalgae.• The method may be used to identify and isolate algicidal molecules affecting algal PSII using a bio-guided isolation protocol.

Highlights

Pulse amplitude modulated (PAM) fluorometry was used to assess over time the effect of different microalgal crude extracts on the efficiency of the photosystem II (PSII) of a tested microalgae (Dunaliella salina)
Pulse amplitude modulated (PAM) fluorometry [1] is a non-destructive method based on chlorophyll a fluorescence that was already successfully used in previous study to assess allelochemical interaction between microalgae [2,3,4], algicidal / antialgal activity of marine bacterium [5] and herbicide activity of chemicals (e.g. Diuron [6])
Photophysiological parameters acquired using PAM fluorometry such as the maximum quantum efficiency of the photosystem II (Fv/Fm) reflects photochemical processes that depend upon chloroplast reactions that use ATP and reductants provided by photosynthesis

Summary

Method Article

A method to assess algicidal activity of microalgal extracts coupling microalgae produced in stirred closed photobioreactor operating in continuous with pulse amplitude modulated (PAM) fluorometry. We couple microalgal production under chemostat cultivation mode to continuously produce a given microalgae species (e.g. Dunaliella salina in this study) at a stable physiological state to ease comparison between extracts tested; with a non-destructive method based on chlorophyll a fluorescence. Pulse amplitude modulated (PAM) fluorometry was used to assess over time the effect of different microalgal crude extracts on the efficiency of the photosystem II (PSII) of a tested microalgae (Dunaliella salina). Method name: Assessment of algicidal effect using PAM fluorometry Keywords: Bioassay, Cytoxicity, Microalgae, Quantum efficiency, Fv/Fm, Non photochemical quenching, NPQ, electron transport rate, Phytochemistry, Anti algal Article history: Received 5 May 2020; Accepted 15 August 2020; Available online 19 August 2020.

Method details

Results validating the method

Conclusion