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In this study the metabolic responses of Botryococcus braunii were analyzed upon different inorganic carbon dosages and nutrient limitation conditions in terms of lipid and biomass productivity, as well as photosynthetic performance. The nutritional schemes evaluated included different levels of sodium bicarbonate and nitrogen and phosphorus starvation, which were contrasted against standard cultures fed with CO2. Bicarbonate was found to be an advantageous carbon source since high dosages caused a significant increase in biomass and lipid productivity, in addition to an enhanced photosynthetic quantum yield and neutral lipids abundance. This contrasts to the commonly used approach of microalgae nutrient limitation, which leads to high lipid accumulation at the expense of impaired cellular growth, causing a decline in overall lipid productivity. The lipidome analysis served to hypothesize about the influence of the nutritional context on B. braunii structural and storage lipid metabolism, besides the adaptive responses exhibited by cells that underwent nutrient stress. [ABSTRACT FROM AUTHOR]

Microalgae biomass exploitation as a carbon–neutral energy source is currently limited by several factors, productivity being one of the most relevant. Due to the high absorption properties of light-harvesting antenna, photosynthetic cells tend to capture an excessive amount of energy that cannot be entirely channeled through the electron transfer chain that ends up dissipated as heat and fluorescence, reducing the overall light use efficiency. Aiming to minimize this hurdle, in this work we studied the effect of decreasing concentrations of Magnesium (Mg2+) on the chlorophyll a content, photosynthetic performance, biomass and lipid production of autotrophic cultures of Botryococcus braunii LB 572. We also performed, for the first time, a comparative lipidomic analysis to identify the influence of limited Mg2+ supply on the lipid profile of this algae. The results indicated that a level of 0.0037 g L−1 MgSO4 caused a significant decline on chlorophyll a content with a concomitant 2.3-fold reduction in the biomass absorption coefficient. In addition, the Mg2+ limitation caused a decrease in the total carbohydrate content and triggered lipid accumulation, achieving levels of up to 53% DCW, whereas the biomass productivity remained similar for all tested conditions. The lipidome analysis revealed that the lowest Mg2+ concentrations also caused a differential lipid profile distribution, with an enrichment of neutral lipids and an increase of structural lipids. In that sense, we showed that Mg2+ limitation represents an alternative optimization approach that not only enhances accumulation of neutral lipids in B. braunii cells but also may potentially lead to a better areal biomass productivity due to the reduction in the cellular light absorption properties of the cells. [ABSTRACT FROM AUTHOR]

Microalgal biomass has been widely investigated as a source of renewable energy, but currently, some alternatives are not economically competitive. Thermochemical conversion of biomass is an alternative way to transform their organic compounds into liquid and gaseous fuels. The aim of this work is twofold; first, the pyrolytic process of the microalga Botryococcus braunii (BB) by thermogravimetric analysis, as well as the relevant reaction kinetic constants and related activation energies, is assessed. Secondly, a sensitivity analysis of the biomass gasification process with air using a thermochemical model was conducted to predict the composition of a syngas as a function of the biomass moisture content and the biomass/air ratio. The results showed that BB biomass is composed mainly of carbon (62.4 wt.%) with volatile solids of 84 wt.%, while the fixed carbon represents around 7 wt.%. Additionally, observed values for heating (27.86 MJ kg−1) and activation energy (~ 110 kJ mol−1) were different from other algal feedstocks due to the capacity of accumulation of liquid hydrocarbons of this. On the other side, the gasification process showed it was found that the moisture content in the biomass and biomass/air ratio variables are key parameters for reaction temperature and producer gas composition. Accordingly, with a suitable combination of these variables, it is possible to obtain a syngas composed of gaseous species with high energy content (CO, 18 vol.%; H2, 17 vol.%; and CH4, 2 vol.%.), which can be transformed through processes such as Fisher-Tropsch process into liquid biofuels such as kerosene or gasoline. [ABSTRACT FROM AUTHOR]

Theobroma cacao is a rich source of flavonoid compounds, which are potent antioxidants. Flavonoids are well-known for their health benefits against cardiovascular diseases, cancer, and improvement of blood pressure. For this reason, cacao mass production has drawn the attention from the functional foods industry. Furthermore, cacao cell suspensions can be used to evaluate complex biosynthetic pathways, such as flavonoids due to the homogeneity of the cell population, the unlimited availability of raw material, the high cell growth and division rates, and the reproducibility of in vitro growth conditions. However, the metabolome of cacao could be affected by exposure to light; especially shorter wavelengths such as blue light trigger targeted flavonoid synthesis. Here, we provide the first report of the metabolomic profile of cacao cell suspensions grown under white-blue and dark conditions. For this, targeted metabolomics was conducted on flavonoids, including bioactive compounds such as catechin, epicatechin and proanthocyanidins (PAs). Moreover, untargeted metabolomics was performed to evaluate the response of the endogenous metabolites exposed to darkness and light. For this, unsupervised and supervised multivariate methods were used. Additionally, a chemical annotation and classification was conducted for the top 50 features obtained from the PLS-DA, in order to identify metabolic pathways that are associated to the light treatments. An increase of glycosylated flavonoids and PAs with higher degrees of polymerization from cells grown under light compared to dark, suggested that light conditions may trigger mechanisms associated with moderate stress. Additionally, lipids, flavonoids, and phytosterols increased after light treatment. The potential of cacao cell suspensions in food biotechnology is discussed, considering that the characterization and quantification of the cacao flavonoid composition are the first steps to evaluate the putative contribution of chocolate to human health. Key message: Metabolomic profiles of cacao cell suspensions under light and dark conditions suggest that flavonoid modification processes could be involved in defense response under light stress. [ABSTRACT FROM AUTHOR]

In recent years, polyphenols from Theobroma cacao and other plant sources have been widely used as natural chemopreventive agents due to their antioxidant properties. Some studies indicate that the polyphenol content, particularly flavan-3-ols, is strongly correlated to the intensity of the purple color in fresh cocoa seeds. However, no visual marker of polyphenol synthesis has been reported in this plant species. The purposes of this study were to monitor the production of certain flavan-3-ols and methylxanthines by chemical and histological analysis in three ecotypes of cacao grown in Colombia at three developmental stages and to compare the result to a standard of polyphenol production over time for two T. cacao cell lines grown in vitro. According to the observations made, polyphenols are stored exclusively in polyphenolic cells that are randomly located between cells that form cotyledon tissue and their biosynthesis is directly proportional to the seed age. Polyphenols are accumulated in the cytoplasm of this kind of cells, which is moved to the protoplasm, coating the cytoplasmic membrane, possibly due to the growth of the vacuole during maturation. In cell culture, polyphenol accumulation is also associated with a particular cell type that is immersed in a group of non-polyphenolic cells. However, it is only possible to identify these cells using destructive staining techniques, which do not allow application of this separation method for obtaining homogenous cell lines. Despite this finding, in this study, it was possible to identify a macroscopic color marker of populations that are rich in dark beige polyphenols, which could be used to screen cell populations. [ABSTRACT FROM AUTHOR]