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Author
Cortiella Valls, Nil
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Abstract
Genetic and metabolic engineering of biological systems allows redirecting cell metabolism to the production of complex biomolecules of interest. Microalgae are unicellular photosynthetic organisms that are emerging as important hosts for industrial biotechnology, as they can use photosynthetic light to efficiently transform CO2 into high value bioproducts, possess GRAS status and capacity to grow in large-scale systems.
Glycolipids are a diverse group of amphipathic molecules that play important biological functions and are attracting industrial interest for a variety of applications, including their use as biodegradable surfactants, in drug-delivery systems, or as bioactive drugs.
Given the ability of microalgae to produce, accumulate and exchange glycolipids between different organelles, we aim to produce added-value glycolipids in the green-cell platform Chlamydomonas reinhardtii, by engineering nuclear and chloroplast genomes.
The main goal of this project is to assess the ability of the cytosol-endoplasmatic compartment to produce a new pool of glycoglycerolipids, alternative to endogenous galactoglycerolipids that are normally present in Chlamydomonas reinhardtii thylakoid membranes. Previous efforts have focused on the heterologous expression in C. reinhardtii of a glycosyltransferase (MG517) from Mycoplasma genitalium, a well-known enzyme is able to produce monoglycosyldiacylglicerol (MGDG) and diglycosyldiacylglicerol (DGDG) when expressed in E. coli. However, when introducing the enzyme in C. reinhardtii showed a poor and unstable expression.
In this study, to test whether this inefficient expression owes to cellular toxicity by the enzyme activity, we have initiated an experiment based on mutagenesis of a catalytically active residue (E193A) to inactivate the enzyme. Additionally, we have initiated an alternative strategy based on the recombineering to clone a variant of the endogenous galactosyldiacylglicerol synthase (MGD1) from Chlamydomonas reinhardtii lacking chloroplast transit peptide. This new construct will allow the cytosolic expression of MGD1 enzyme in the cytosol of the green microalgae thus producing a new pool of glycolipids in the cell.
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