“Green microalgae biohydrogen production”

Nowadays, renewable energy is one of the most discussed issues by the international scientific community. The unrestrained use of fossil fuels has raised relevant questions about sustainability and effects on the environment. Hydrogen (H2) is considered a promising fuel due to its thermodynamical properties and CO2-free combustion. Nevertheless, environmental problems arise when H2 is produced using energy deriving from fossil sources: only “green hydrogen” identifies a production 100% based on renewable energy. Currently, several microorganisms are known for their ability to produce H2 as a metabolic feature. Regarding microalgae, most of the information comes from Chlamydomonas reinhardtii. In this green microalgae, two different photosynthetic production pathways and one fermentative-like metabolism have been described concerning transitory H2 production. To extend H2 production one requirement is the creation of a hypoxic environment. This occurs when photosynthetic activity slows down or if there is an increase in mitochondrial respiration rates. Moreover, the electron flow should be directed preferentially towards the H2 evolution enzyme, hydrogenase. Concerning physiological conditioning, one of the most promising strategies for H2 production is sulphur deprivation from cultivation medium: within three days, anaerobiosis develops under saturated light. Chlamydomonas has also represented an excellent example for the development of different molecular strategies, that allow to overcome some limitations and extend the H2 production. One of the limitations is related to sunlight saturation and dissipation that also affect H2 production. Mutants with the truncated light-harvesting antenna (tla) in the chloroplast are subject to fewer phenomena of photoinhibition and light saturation. Another limitation is linked to the competitive pathways that remove electrons from hydrogenase. Pgrl1 (protein gradient regulation like 1) mutant showed improved H2 production reducing this phenomenon. Another relevant issue is the oxygen sensitivity of the hydrogenase enzyme. The use of an O2-tolerant clostridial [FeFe]-hydrogenase, expressed in C. reinhardtii, showed better enzymatic rate, as the bacterial hydrogenase had a lower inactivation rate in aerobiosis. The work carried out over the past three years was aimed primarily at the isolation and characterization of microalgal species in the Basilicata region for the identification of new biohydrogen producers. Particular attention has been given to the search for strains with good growth rates and able to use different carbon sources. Secondly, the physiological behaviour of single and double mutants of Chlamydomonas was analyzed concerning H2 production by modulating light condition without resorting to stress application, such as sulphur deprivation. Freshwater samples collected in different villages of the Basilicata region were used to isolate microalgae with different morphologies. Microscopical observations and molecular identification made it possible to identify the genus of the isolated pure colonies. The growth of the various strains was followed by different methods: absorbance and chlorophyll content proved to be effective and fast for monitoring cell growth over the days. This made it possible to evaluate the growth rates of the species under examination. Various tests were carried out to detect the production of H2. Bioreactors were kept in dark, limited light (12 PAR) or sulfur deprivation (with intense light, 100 PAR). All the experiments considered different carbon source too. The levels of H2 gas produced were daily assessed by gas chromatography by taking a sample of the airspace in contact with the liquid culture in the airtight bioreactors. Desmodesmus sp. and Haematococcus sp. strains demonstrated production of H2 similar to wild type Chlamydomonas (5-10 ml/litre of culture). Furthermore, the same production occurred similarly using acetate or glucose. For Chlamydomonas mutants, the experiments were conducted in collaboration with the University of Córdoba (Spain). Investigated mutants were tla3, pgrl1, and one engineered with Clostridium bacterial hydrogenase (clostr) and the relative combinations tla3 + pgrl1 and clostr + pgrl1 from genetic cross. In this case, the wild type, single and double mutant strains were subjected to different lighting conditions (12, 50, 100, 450 PAR). In particular, the combination tla3 + pgrl proved to be the best as it is capable of producing H2 even at light intensities that are generally less tolerated, opening up new application scenarios. The single mutant Clostr showed instead a fast hydrogenase activity in a replete media also proportionally with the increase of light. In conclusion, the algae isolated during the PhD project have shown interesting implications for the production of H2 such as the metabolic versatility regarding the use of the different carbon sources. This leads to the need to carry out a more in-depth investigation of the mechanisms underlying the metabolism of these microalgae both from a physiological and a molecular point of view. Regarding single and double Chlamydomonas mutants, knowledge about their behaviour in different light conditions and the feasibility of H2 production has been expande

An innovative protocol to select the best growth phase for astaxanthin biosynthesis in H. pluvialis.

H. pluvialis is a green unicellular microalgae and it is the first producer of natural astaxanthin in the world if subjected to stress conditions such as high light, high salinity and nutrient starvation. Astaxanthin is a powerful antioxidant used in many fields, such as aquaculture, pharmaceutical, food supplements and cosmetic. To obtain a large amount of astaxanthin, researcher focused on the optimisation of H. pluvialis growth. H. pluvialis has four different size growth stage (macrozooids, microzooids, palmelloid and “red non-motile astaxanthin accumulated encysted”), and astaxanthin production occur in the last phase. Recent studies shown that non-motile cells can produce more astaxanthin than motile cells if subjected to light stress. For these reasons, the aim of this study is to find a new and innovative methodology to select and recovery H. pluvialis in his last growth phase thanks to an electrophoretic run, and optimize, in this way, astaxanthin production

Lipids from Microalgae for Cosmetic Applications

In recent years, there has been considerable interest in using microalgal lipids in the food, chemical, pharmaceutical, and cosmetic industries. Several microalgal species can accumulate appreciable lipid quantities and therefore are characterized as oleaginous. In cosmetic formulations, lipids and their derivatives are one of the main ingredients. Different lipid classes are great moisturizing, emollient, and softening agents, work as surfactants and emulsifiers, give consistence to products, are color and fragrance carriers, act as preservatives to maintain products integrity, and can be part of the molecules delivery system. In the past, chemicals have been widely used but today’s market and customers’ demands are oriented towards natural products. Microalgae are an extraordinary source of lipids and other many bioactive molecules. Scientists’ attention to microalgae cultivation for their industrial application is increasing. For the high costs associated, commercialization of microalgae and their products is still not very widespread. The possibility to use biomass for various industrial purposes could make microalgae more economically competitive

Transcriptomic response to nitrogen availability reveals signatures of adaptive plasticity during tetraploid wheat domestication

: The domestication of crops, coupled with agroecosystem development, is associated with major environmental changes and provides an ideal model of phenotypic plasticity. Here, we examined 32 genotypes of three tetraploid wheat (Triticum turgidum L.) subspecies, wild emmer, emmer and durum wheat, which are representative of the key stages in the domestication of tetraploid wheat. We developed a pipeline that integrates RNA-Seq data and population genomics to assess gene expression plasticity and identify selection signatures under diverse nitrogen availability conditions. Our analysis revealed differing gene expression responses to nitrogen availability across primary (wild emmer to emmer) and secondary (emmer to durum wheat) domestication. Notably, nitrogen triggered the expression of twice as many genes in durum wheat compared to that in emmer and wild emmer. Unique selection signatures were identified at each stage: primary domestication mainly influenced genes related to biotic interactions, whereas secondary domestication affected genes related to amino acid metabolism, in particular lysine. Selection signatures were found in differentially expressed genes, notably those associated with nitrogen metabolism, such as the gene encoding glutamate dehydrogenase. Overall, our study highlights the pivotal role of nitrogen availability in the domestication and adaptive responses of a major food crop, with varying effects across different traits and growth conditions

Effects of astaxanthin in animal models of obesity-associated diseases: a systematic review and meta-analysis.

Background and aim: Obesity is a major risk factor for several diseases, including metabolic syndrome (MetS), non-alcoholic fatty liver disease (NAFLD) and type 2 diabetes (T2D). The use of natural products, such as astaxanthin (ASX), a potent antioxidant compound produced by the freshwater green microalga Haematococcus pluvialis, has gained particular interest to reduce oxidative stress and inflammation, and to improve redox status, often associated with obesity. A systematic review and meta-analysis was performed to comprehensively examine the effects of ASX in animal models of diet induced obesity-associated diseases in order to inform the design of future human clinical studies for ASX use as supplement or nutraceutical. Methods: Cinahl, Cochraine, MEDLINE, Scopus and Web of Science were searched for English-language manuscripts published between January 2000 and April 2020 using the following key words: astaxanthin, obesity, non-alcoholic fatty liver disease, diabetes mellitus type 2, NAFLD and metabolic. Results: Seventeen eligible articles, corresponding to 21 animal studies, were included in the final quantitative analysis. ASX, at different concentrations and administered for different length of time, induced a significant reduction in adipose tissue weight (P=0.05) and systolic blood pressure (P[less than]0.0001) in control animals. In animal models of T2D, ASX significantly reduced serum glucose levels (P=0.04); whereas it improved several disease biomarkers in the blood (e.g. cholesterol, triglycerides, ALT and AST, P[less than]0.10), and reduced liver (P=0.0002) and body weight (P=0.11), in animal models of NAFLD. Conclusions: Supplementation of ASX in the diet has positive effects on symptoms associated with obesity related diseases in animals, by having lipid-lowering, hypo-insulin and hypoglycaemic capacity, protecting organs from oxidative stress and mitigating the immune system, as suggested in this review

Biohydrogen from Microalgae: Production and Applications

The need to safeguard our planet by reducing carbon dioxide emissions has led to a significant development of research in the field of alternative energy sources. Hydrogen has proved to be the most promising molecule, as a fuel, due to its low environmental impact. Even if various methods already exist for producing hydrogen, most of them are not sustainable. Thus, research focuses on the biological sector, studying microalgae, and other microorganisms’ ability to produce this precious molecule in a natural way. In this review, we provide a description of the biochemical and molecular processes for the production of biohydrogen and give a general overview of one of the most interesting technologies in which hydrogen finds application for electricity production: fuel cells

Transcriptomic response to nitrogen availability reveals signatures of adaptive plasticity during tetraploid wheat domestication

Scripts used in this study are available at Github https://github.com/PapaLab/transcriptomics_triticum.git. The RNA-Seq libraries generated and analyzed in this study have been deposited in the Sequence Read Archive (SRA) of the National Center of Biotechnology Information (NCBI) under BioProject number PRJNA1015013. The nucleotide sequences of all discussed genes are available on the GarinGenes Database (https://wheat.pw.usda.gov/cgi-bin/GG3/browse.cgi) and can be accessed using the Gene model IDs provided in the Supplementary Data Sets (e.g. TraesCS2A03G0941300).International audienceThe domestication of crops, coupled with agroecosystem development, is associated with major environmental changes and provides an ideal model of phenotypic plasticity. Here, we examined 32 genotypes of three tetraploid wheat (Triticum turgidum L.) subspecies, wild emmer, emmer, and durum wheat, which are representative of the key stages in the domestication of tetraploid wheat. We developed a pipeline that integrates RNA-Seq data and population genomics to assess gene expression plasticity and identify selection signatures under diverse nitrogen availability conditions. Our analysis revealed differing gene expression responses to nitrogen availability across primary (wild emmer to emmer) and secondary (emmer to durum wheat) domestication. Notably, nitrogen triggered the expression of twice as many genes in durum wheat compared to that in emmer and wild emmer. Unique selection signatures were identified at each stage: primary domestication mainly influenced genes related to biotic interactions, whereas secondary domestication affected genes related to amino acid metabolism, in particular lysine. Selection signatures were found in differentially expressed genes (DEGs), notably those associated with nitrogen metabolism, such as the gene encoding glutamate dehydrogenase (GDH). Overall, our study highlights the pivotal role of nitrogen availability in the domestication and adaptive responses of a major food crop, with varying effects across different traits and growth conditions