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

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.

The effects of CO2-induced acidification on Tetraselmis biomass production, photophysiology and antioxidant activity: A comparison using batch and continuous culture

“…Under both pH conditions in the batch culture, Fv/Fm increased during the exponential growth phase to stabilize and decrease once the stationary phase was reached. The Fv/Fm values are similar to those previously measured for eukaryotic microalgae cultivated in similar culture conditions (Barnett et al, 2015;Goiris et al, 2015b;Jauffrais et al, 2016;Menguy et al, 2020). Yet, Fv/Fm reached a lower maximum value and decreased faster at pH 6.5 compared to pH 8.5.…”

Heterocapsa cf. bohaiensis (dinoflagellate): identification and response to nickel and iron stress revealed through chlorophyll a fluorescence

“…Cultures were carried out in three 10-L stirred closed photobioreactors (PBRs) made of transparent polymethylmethacrylate (Menguy et al 2020). The pH was maintained at 8.2 using automated CO2 injections and the temperature was kept constant at 26°C by thermal exchange.…”

“…Environmental and culture conditions highly influence microalgae physiology which will affect their growth and photosynthetic efficiency. The PSII efficiency is therefore a good marker of microalgae fitness under abiotic stresses such as metallic trace elements (Coulombier et al 2020, Menguy et al 2020, Wang et al 2023. PAM fluorometry is a commonly used technique to assess PSII efficiency in microalgae (Antal et al 2009) and has the advantage of being reliable, fast, and noninvasive (Schreiber et al 1995).…”