Evaluation of light quality, temperature and nutritive deprivation impact onto starch accumulation in Chlorella vulgaris
Creators: name: Six, A.
name: Fleury, G.
name: Alvarez, P.
name: Delrue, F.
name: Fon-Sing, S.
name: Compadre, A.
name: Dimitriades-Lemaire, A.
name: Dauvillée, D.
name: Petroutsos, D.
name: Li-Beisson, Y.
name: Sassi J.-F
Publisher: name: Zenodo
Year: 2022
Subjects: Chlorella vulgaris
Physiological stress
Nutrient deprivation
Supra-optimal temperature
Light quality
Starch
Amylose
Bioplastics

description: SEALIVE (1) and Nenu2PHAr (2) European projects are both dedicated to produce biodegradable and biosourced plastics. Microalgae can provide material for the manufacture of plastics currently obtained from petrol or food crop (3). Starch is notably used as a natural biopolymer base to be integrated in plastics blends (4), and can also be degraded into monomeric glucose to feed PHA producing bacteria (5). Several external factors act as signals to redirect the metabolism towards the production, polymerization and storage of glucose (6). Notably, nutrient depletion is known to promote both carbohydrates and lipid pathways. However, in a continuous culture mode, nutrient removal from culture media can be difficult to achieve and other stress inducers might be preferred. Recently, other types of stress have been shown to lead to starch accumulation in green microalgae (7)<em>.</em> Supra-optimal temperatures were shown to trigger starch accumulation in <em>Parachlorella kessleri</em> and <em>Chlamydomonas reinhardtii </em>(7) (8). The depletion of blue light from the light spectrum was described as a carbohydrates enhancing factor in <em>C. reinhardtii </em>(9). <em>Chlorella vulgaris </em>CCALA924 was identified as a high starch producer relevant for industrial scale cultivation (10). This strain was described to accumulate starch up to 60% of dry weight when submitted to a physiological stress. Here, its ability to accumulate starch under nutrient deprivation, high temperature or blue light free spectra was tested and content of at least 40% of starch was obtained at laboratory scale. Interestingly, starch structure had almost no amylose when produced under blue light free spectra, whereas nutrient deprivation and high temperature conditions lead to 15% of amylose. These lab results should be tested at pilot scale in order to evaluate the technico-economical relevancy of those new means of producing starch in microalgae.
description: Half a PhD Grant provided to A. Six by RegionSUD,
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