Espace Presse – Microalgae for biofuels

An alternative to fossil fuels in the mobility and petrochemical sector?

The oils that microalgae produce
by photosynthesis (glycerolipids), constitute energy reserves that can be converted

biofuelsby chemical way.

Advantage : a neutral balance in CO2the carbon dioxide released by the spent fuel is compensated by that absorbed by the plant.

Inconvenience : In order to transform this solution into an economically viable industrial process, a few obstacles still need to be overcome, especially those relating to the growth rate of microalgae and their oil productivity.

At the CEA, several units are involved in this project: the Interdisciplinary Research Institute of Grenoble (Irig), the Institute of Biosciences & Biotechnology of Aix-Marseille (BIAM) as well as the local CEA Tech Paca facility.

The research conducted on Irig is presented to you below.

Better understand how microalgae work

We work with marine and terrestrial microalgae. Unknown, they nevertheless have great potential. »Eric Maréchal, Laboratory Manager

For the Irig teams, it’s a full understanding of how microalgae work
essential condition. Their molecular and cellular mechanisms (which control photosynthesis), cellular architecture, carbon metabolism (it produces all living molecules from CO2) as well as their reactions to environmental variations are actually still very poorly understood. To remedy this, researchers are deciphering the functions of genes involved in these mechanisms.

Collection of microalgae, including marine and terrestrial species, which cover a biodiversity ranging from green algae, red algae, diatoms, eustigmatophytes to certain non-photosynthetic species.

How ?
In omics technologies: genomics (analysis of genes), transcriptomics (analysis of messenger RNAs), proteomics (analysis of proteins), lipidomics (analysis of lipids). This new knowledge is used to develop lines of microalgae that are optimized for the production of energy oils.

Improvement of microalgae lines through genetic engineering

Each step in genetic engineering aims to understand and optimize the properties of our microalgae. »Juliette Salvaing (Inrae), researcher

It is through genetic engineering that scientists are improving lines of microalgae so that they
produce more oils while having optimal growth. Thanks to the genetic editing tool Crispr-Cas9, a kind of molecular scissors, they create specific modifications in
genes of interestinvolved, for example, in a metabolic pathway, a regulatory system, a molecular complex, etc.


Comparison of control and genetically engineered microalgae colonies. © L. Godart / CEA

Researchers also use these genes of interest as search criteria to select new species of microalgae in public collections and in all environmental areas (snow, hot springs, oceans, etc.).

Biofuels for whom?

The market for biofuels is primarily aimed at large carriers: aircraft, boats, heavy trucks. Not very suitable for electric propulsion, due to the volume of the batteries and short autonomy, these modes of transport still require liquid fuel. Biofuels supplied by microalgae are among the low-carbon alternatives studied, in addition to other sources of biomass.

Choose the strongest and most productive algae

The algae we select must be stable in relation to the growing conditions and produce oils with high energy potential. »Juliette Jouhet (CNRS), Head of the Lipang Platform

Researchers select the most productive strains and ensure their robustness, ie
maintain their productivity (quantity and quality of oils produced per liter and per day)
depending on growth conditionsand. For this they have, in addition to a number of climatic chambers, a
analytical platform called Lipang (Lipid analysis in Grenoble).


The microalgae are grown in a sterile liquid medium, with stirring, inside lit and thermostatically controlled climatic chambers. © L. Godart / CEA

unique in France enables the most accurate and exhaustive qualification of the various glycerolipids present in a sample: extraction, identification, structural analysis, quantification, etc. The whole metabolic chain is thus finely analyzed, including the precursor molecules in the oils and those resulting from them. .

Preparation for industrialization

We are still in a research phase. Feedback from industry is crucial to optimize both tribes and cultural processes. »Alberto Amato, CEA researcher in genetic engineering.

It is also necessary to transform the cultivation process developed in the laboratory
into an industrial system, implemented on a larger scale. In a photobioreactor that partially mimics industrial conditions, researchers play on the concentrations, the media, the supply of CO2, etc. to optimize crops. Because oils are only produced under stressful conditions.


Cultivation in a photobioreactor. This system makes it possible to compare the performance obtained in flasks grown in climatic chambers with those measured under conditions that mimic certain pre-industrial pilot systems. © L. Godart / CEA

The challenge is therefore to find the right compromise between stress (eg lack of nutrients) and rapid algae growth. The optimized strains and processes are then
transferred to the industrialist, here TotalEnergieswhich evaluates the scaling.

Elsewhere at CEA

The teams from the Institute of Biosciences & Biotechnology of Aix-Marseille (BIAM) from CEA and CEA Tech Paca are particularly interested in the production of volatile hydrocarbons in the gaseous phase of the algae culture medium, especially thanks to the expression of a promising enzyme they discovered, Fatty -Acid Photodecarboxylase. This makes it possible to convert certain fatty acids from the microalgae to hydrocarbons using light energy.

This article appeared in Les Défis du CEA No. 247

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