Improving Microalgae Research and Marketing in the European Atlantic Area: Analysis of Major Gaps and Barriers Limiting Sector Development.

Microalgae and cyanobacteria represent a diverse renewable resource with significant potential for the industrial production of goods and services with high added value. However, scientific, technical/technological, legislative and market gaps and barriers still limit the growth of these markets in Europe and the number of exploited species. We conducted an in-depth survey of European microalgae researchers, experts and stakeholders to identify these limitations and to discuss strategies, recommendations and guidelines to overcome these barriers. Here, we present the findings of this study which detail the main promising markets for microalgae and cyanobacteria in the coming decades, an updated SWOT analysis of the sector, the current opportunities, limitations, risks and threats for microalgae research and market sectors in Europe, a traffic light analysis for a quick assessment of market opportunities for each microalgae sector and detailed recommendations/guidelines for overcoming the scientific, technical/technological, legislative and market gaps and barriers.

Analysis of Scientific Research Driving Microalgae Market Opportunities in Europe.

A bibliographic database of scientific papers published by authors affiliated to research institutions worldwide, especially focused in Europe and in the European Atlantic Area, and containing the keywords "microalga(e)" or "phytoplankton" was built. A corpus of 79,020 publications was obtained and analyzed using the Orbit Intellixir software to characterize the research trends related to microalgae markets, markets opportunities and technologies that could have important impacts on markets evolution. Six major markets opportunities, the production of biofuels, bioplastics, biofertilizers, nutraceuticals, pharmaceuticals and cosmetics, and two fast-evolving technological domains driving markets evolution, microalgae harvesting and extraction technologies and production of genetically modified (GM-)microalgae, were highlighted. We here present an advanced analysis of these research domains to give an updated overview of scientific concepts driving microalgae markets.

A Bibliometric Analysis of Microalgae Research in the World, Europe, and the European Atlantic Area.

：A bibliographic database of scientific papers published by authors affiliated worldwide, especially focused in Europe and in the European Atlantic Area, and containing the keywords "microalga(e)" or "phytoplankton" was built. A corpus of 79,020 publications was obtained and analyzed using the Orbit Intellixir software to highlight the evolution of the research domain. Publication rates from 1960 to 2019, organization of the research, collaboration networks between countries and organizations, emerging and fading research concepts, major studied species, and associated concepts, as well as journals publishing microalgae research were considered. As a result, of the 79,020 papers published worldwide, 26,137 included authors from Europe (33% of world production) and 6989 from the European Atlantic Area (AA) (27% of European production, 9% of world production). The main worldwide scientific research topics found in this study were phytoplankton, community, bloom, diatoms, distribution, ecosystem, coastal, chlorophyll, zooplankton, photosynthesis, and primary production. At the European scale, the most studied topics were related to the environment, food, chemicals, pigments, protein, feed, and drugs. The highest scientific trends and market opportunities analysis identified bioplastics and biostimulants as top emerging concepts at the European level and agricultural, animal feed, and blue biotechnology at the European AA level.

Metabolic, Physiological, and Transcriptomics Analysis of Batch Cultures of the Green Microalga Chlamydomonas Grown on Different Acetate Concentrations.

Acetate can be efficiently metabolized by the green microalga Chlamydomonasreinhardtii. The regular concentration is 17 mM, although higher concentrations are reported to increase starch and fatty acid content. To understand the responses to higher acetate concentrations, Chlamydomonas cells were cultivated in batch mode in the light at 17, 31, 44, and 57 mM acetate. Metabolic analyses show that cells grown at 57 mM acetate possess increased contents of all components analyzed (starch, chlorophylls, fatty acids, and proteins), with a three-fold increased volumetric biomass yield compared to cells cultivated at 17 mM acetate at the entry of stationary phase. Physiological analyses highlight the importance of photosynthesis for the low-acetate and exponential-phase samples. The stationary phase is reached when acetate is depleted, except for the cells grown at 57 mM acetate, which still divide until ammonium exhaustion. Surprisal analysis of the transcriptomics data supports the biological significance of our experiments. This allows the establishment of a model for acetate assimilation, its transcriptional regulation and the identification of candidates for genetic engineering of this metabolic pathway. Altogether, our analyses suggest that growing at high-acetate concentrations could increase biomass productivities in low-light and CO2-limiting air-bubbled medium for biotechnology.

Continuous selection pressure to improve temperature acclimation of Tisochrysis lutea.

Temperature plays a key role in outdoor industrial cultivation of microalgae. Improving the thermal tolerance of microalgae to both daily and seasonal temperature fluctuations can thus contribute to increase their annual productivity. A long term selection experiment was carried out to increase the thermal niche (temperature range for which the growth is possible) of a neutral lipid overproducing strain of Tisochrysis lutea. The experimental protocol consisted to submit cells to daily variations of temperature for 7 months. The stress intensity, defined as the amplitude of daily temperature variations, was progressively increased along successive selection cycles. Only the amplitude of the temperature variations were increased, the daily average temperature was kept constant along the experiment. This protocol resulted in a thermal niche increase by 3°C (+16.5%), with an enhancement by 9% of the maximal growth rate. The selection process also affected T. lutea physiology, with a feature generally observed for 'cold-temperature' type of adaptation. The amount of total and neutral lipids was significantly increased, and eventually productivity was increased by 34%. This seven month selection experiment, carried out in a highly dynamic environment, challenges some of the hypotheses classically advanced to explain the temperature response of microalgae.

The use of fluorescent Nile red and BODIPY for lipid measurement in microalgae.

Microalgae are currently emerging as one of the most promising alternative sources for the next generation of food, feed, cosmetics and renewable energy in the form of biofuel. Microalgae constitute a diverse group of microorganisms with advantages like fast and efficient growth. In addition, they do not compete for arable land and offer very high lipid yield potential. Major challenges for the development of this resource are to select lipid-rich strains using high-throughput staining for neutral lipid content in microalgae species. For this purpose, the fluorescent dyes most commonly used to quantify lipids are Nile red and BODIPY 505/515. Their fluorescent staining for lipids offers a rapid and inexpensive analysis tool to measure neutral lipid content, avoiding time-consuming and costly gravimetric analysis. This review collates and presents recent advances in algal lipid staining and focuses on Nile red and BODIPY 505/515 staining characteristics. The available literature addresses the limitations of fluorescent dyes under certain conditions, such as spectral properties, dye concentrations, cell concentrations, temperature and incubation duration. Moreover, the overall conclusion of the present review study gives limitations on the use of fluorochrome for screening of lipid-rich microalgae species and suggests improved protocols for staining recalcitrant microalgae and recommendations for the staining quantification.