The impact of light supply to moving photosynthetic biofilms
| Type | : | ACL |
|---|---|---|
| Nature | : | Production scientifique |
| Au bénéfice du Laboratoire | : | Oui |
| Statut de publication | : | Publié |
| Année de publication | : | 2019 |
| Auteurs (4) | : | GRENIER Jérôme BONNEFOND Hubert LOPES Filipa BERNARD Olivier |
| Revue scientifique | : | Algal Research |
| Volume | : | 44 |
| Fascicule | : | |
| Pages | : | |
| DOI | : | 10.1016/j.algal.2019.101674 |
| URL | : | http://www.sciencedirect.com/science/article/pii/s2211926418303655 |
| Abstract | : | The production of microalgae using biofilm-based processes is becoming popular because of their higher pro-ductivity compared to traditional culture systems. Another advantage of microalgal biofilms is the straightfor-ward harvesting procedure achieved by scraping offthe biofilm, significantly reducing the energy demand re-quired when concentrating liquid culture. Here, a promising way to grow microalgae is explored, examining abiofilm developed on a moving conveyor belt. Algae are then successively exposed to light and dark periods asthe conveyer belt rotates. A lab-scale biofilm-based reactor mimicking the light pattern of the moving system wasfirst used to study the effect of light/dark cycles on aChlorella autotrophicabiofilm. The succession of light anddark phases (in the order of minutes) effectively dilutes the light over a given time period and mitigates over-exposure of light, which can lead to photoinhibition. When the illumination time represents one-third of thecycle period (light dilution factor of 3), the biofilm seems to deal with photoinhibition better than when thebiofilm is exposed to permanent illumination. Extrapolations for a rotating conveyer belt in such conditionspoints out twofold productivity compared to a static biofilm exposed to continuous light. However, when theperiods in the dark extend too long, respiration decreases the carbon pool, hindering the benefit of photo-synthesis, and a trade-offmust be achieved.1. IntroductionThe tremendous potential of microalgae has been highlightedthrough the last decade [1,2] with applications for high added valuemolecules such as antioxidants, antibacterial products, pigments andpolyunsaturated fatty acids, but also for the markets of food or feed, aswell as for waste treatments (gaseous and liquid). Moreover, somemicroalgal (or cyanobacteria) species can store large fractions of tria-cylglycerol (TAG) or carbohydrates (especially after N or P depriva-tion), which can be turned into biodiesel or bioethanol, respectively.These have been identified as a potential renewable source for biofuelproduction [3]. These aquatic organisms can be mass cultivated inclosed photobioreactors or open-ponds using solar radiation, so thatproduction may become sustainable with reduced environmental costs[4].Microalgae have several advantages compared to terrestrial plants,but the most significant feature is that they can grow at a substantiallyhigh rate, with potential productivities one order of magnitude largerthan terrestrial plants and without using agricultural land [2–4].However, the outdoor productivities recorded so far turn out to bedisappointing and are often well below the theoretical maximum (thetheoretical maximum efficiency of solar energy conversion is approxi-mately 11%) [5]. This is probably due to the immaturity of this bio-technologicalfield, where significant amounts of progress are expectedat each step of the process (e.g., strain selection, reactor design andoperation and downstream processing). However, more fundamentally,the difficulty in achieving optimal productivities for outdoor systemsresults from the intricate interaction of nonlinear and dynamical phe-nomena that profoundly affect growth. In particular, when grown inoutdoor facilities, microalgae are submitted to mostly suboptimal lightand temperature conditions [6].The frequency and time of exposition to high light strongly affectmicroalgae growth. Several studies have reported an increase in bio-mass productivity, for the same daily dose, when rapid light/dark cy-cles (flashing light) are applied in conventional microalgae cultures[7, 8]. When cells stay too long in the illuminated part of the culturedevice, they become photo-saturated or even photo-inhibited. Indeed,when excited, reaction centres receive additional photons, and as ahttps://doi.org/10.1016/j.algal.2019.101674Received 8 May 2018; Received in revised form 18 September 2019; Accepted 18 September 2019⁎Corresponding author at: Université Paris-Saclay, CentraleSupélec, Laboratoire de Génie des Procédés et Matériaux LGPM, 3 rue Joliot Curie, 91160 Gif-sur-Yvette, France.E-mail address:jerome.grenier60@gmail.com(J. Grenier).Algal Research 44 (2019) 101674Available online 05 November 20192211-9264/ © 2019 Elsevier B.V. All rights reserved.T |
| Mots-clés | : | Microalgae; Biofilm; Light alternation; Chlorella autotrophica; Rotating algal systems; Photoacclimation |
| Commentaire | : | - |
| Tags | : | - |
| Fichier attaché | : | - |
| Citation | : |
Grenier J, Bonnefond H, Lopes F, Bernard O (2019) The impact of light supply to moving photosynthetic biofilms. Algal Res 44 | doi: 10.1016/j.algal.2019.101674
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