| dc.description.abstract | Even if the commercial potential of microalgae is widely recognized, industrial applications are still limited due to high production costs. For commercialization to be feasible, increasing the biological productivity of the system is a major challenge to surpass. To this end, this thesis aimed to identify, and possibly overcome, a set of bottlenecks connected to the "light-to-biomass" conversion in microalgae. We use two main strategies to achieve this: 1) using genetic engineering to identify key metabolic pathways that can be targeted; 2) exploring the natural diversity of microalgae with the aim to identify strains with desirable traits. The possibility to create Truncated Light harvesting Antenna (TLA)-strains, to increase biomass productivity, was investigated in the pennate diatom Phaeodactylum tricornutum. By using CRISPR/Cas9 we targeted proteins predicted to be involved in the Chloroplast signal recognition particle pathway (CpSRP). Knocking out ALBINO3b (ALB3b) led to a major decrease of the main light harvesting complex (LHC) proteins. The alb3b mutant lines show all the characteristics related to TLA-strains. Absence of the GTPase CpSRP54, however, did not cause any decrease in LHC proteins but led to a high light sensitive phenotype. This indicates that, in diatoms, LHC proteins are targeted to the thylakoid membranes in a CpSRP independent manner. We investigated the pigment-protein environment of the remaining antenna in the alb3b mutant lines and show that a functional rearrangement of LHC proteins takes place, in order to preserve the presence of a functional peripheral FCP antenna. Microalgae are a highly diverse group of organisms, that potentially harbor a wide range of bio-compounds that could be of interest for industries. However, the identification of strains of interest depends on the existence of adequate screening tools. Here we presented Nanocosm, a versatile LED-based micro-scale photobioreactor (PBR) that allows simultaneous testing of multiple variables in a fast and cheap way. This system was used to identify strains naturally capable of withstanding the extreme light conditions in a PBR. We investigated the effect of a fluctuating light (FL) regime, mimicking the light perception of one cell in a PBR, on 19 eco-types of the chain forming diatom Skeletonema marinoi. We were able to identify strains performing very good under FL conditions that can potentially be of interest for industrial applications. The strains performing better under the FL conditions shared some common photo-acclimation and photo-protection strategies that might be the results of adaptation to the specific environment of origin. | en_US |
