Investigation of quinone reduction by microalgae using fluorescence - do “lake” and “puddle” mechanisms matter?

Fluorescence data for investigating the ability of quinones to extract photosynthetic electrons are revisited in the case of microalgae. In particular, two light capture mechanisms (lake vs. puddle) are considered which plays an important role in how to quantify the effect of quinones. The results for both mechanisms are compared and the best way to assess the effect of quinones is discussed. [Display omitted] •Fluorescence data on the quinone reduction by photosynthetic algae were revisited.•The electron harvesting by quinones was derived via two light capture mechanisms.•«Lake» and «Puddle» mechanisms play a role on the quinone efficiency.•The harvesting efficiencies remain in line with the redox potentials of quinones.•Previous fluorescence analyses on this photobioelectrochemical system remain valid. Photosynthesis is a fundamental process used by Nature to convert solar energy into chemical energy. For the last twenty years, many solutions have been explored to provide electrical power from the photosynthetic chain. In this context, the coupling between microalgae and exogenous quinones is an encouraging strategy because of the capability of quinones to be reduced by the photosynthetic chain. The ability of a quinone to be a good or bad electron acceptor can be evaluated by fluorescence measurements. Fluorescence analyses are thus a convenient tool helping to define a diverting parameter for some quinones. However, this parameter is implicitly designed on the basis of a particular light capture mechanism by algae. In this paper, we propose to revisit previous fluorescence experimental data by considering the two possible mechanisms (lake vs. puddle) and discussing their implication on the conclusions of the analysis. In particular, we show that the maximum extraction efficiency depends on the mechanism (in the case of 2,6-dichlorobenzoquinone – 2,6-DCBQ, (0.45 ± 0.02) vs (0.61 ± 0.03) for lake and puddle mechanisms respectively) but that the trends for different quinones remain correlated to the redox potentials independently of the mechanism.