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Microalgae are promising feedstock for renewable fuels. The accumulation of oils in microalgae can be enhanced by nanoparticle exposure. However, the nanoparticles employed in previous studies are mostly non-biodegradable, which hinders nanoparticles developing as promising approach for biofuel production. We recently reported the engineered resin nanoparticles (iBCA-NPs), which were found to be biodegradable in this study. When the cells of green microalga Chlamydomonas reinhardtii were exposed to the iBCA-NPs for 1 h, the cellular triacyclglycerols (TAG) and starch contents increased by 520% and 60% than that in the control. The TAG production improved by 1.8-fold compared to the control without compromised starch production. Additionally, the content of total fatty acids increased by 1.3-fold than that in control. Furthermore, we found that the iBCA-NPs addition resulted in increased cellular reactive oxygen species (ROS) content and upregulated the activities of antioxidant enzymes. The relative expressions of the key genes involved in TAG and starch biosynthesis were also upregulated. Overall, our results showed that short exposure of the iBCA-NPs dramatically enhances TAG and starch accumulation in Chlamydomonas, which probably resulted from prompt upregulated expression of the key genes in lipid and starch metabolic pathways that were triggered by over-accumulated ROS. This study reported a useful approach to enhance energy-rich reserve accumulation in microalgae. Key points: 1. The first attempt to increase oil and starch in microalgae by biodegradable NPs. 2. The biodegradability of iBCA-NPs by the BOD test was more than 50% after 28 days. 3. The iBCA-NPs induce more energy reserves than that of previously reported NPs. [ABSTRACT FROM AUTHOR]

Monogalactosyldiacylglycerols (MGDGs) have potential applications in food products, cosmetics and pharmaceuticals. MGDGs from microalgae with high amounts of polyunsaturated fatty acids (PUFAs) have potential functions, which arise the interest of the researchers. MGDGs were prepared by silica gel column chromatography with the appropriate mobile phase, while due to the similarity to molecular structure of MGDGs, digalactosyldiacylglycerols (DGDGs) were the most difficult impurities to separate during the extraction process of MGDGs from Nannochloropsis oceanica IMET1 and Arthrospira platensis. In order to obtain MGDGs from microalgae using low toxic solvent system, a novel material Click thiol-ene cysteine (Click TE-Cys) was employed to achieve its selective separation by differentiation of the hydrophilic interaction. The mixture of MGDGs and DGDGs standards were separated from each other by Click TE-Cys solid phase extraction (SPE), which was further confirmed by the result of LC-MS. The molecular interaction of MGDGs and DGDGs with Click TE-Cys demonstrated that DGDGs had more hydrogen bonds with Click TE-Cys material, which might cause a higher hydrophilic interaction. In this study, the Click TE-Cys material exhibited higher hydrophilicity with DGDGs and effectively separated MGDGs from 4 species microalgae by 'flow-through' mode using ethanol as mobile phase. [ABSTRACT FROM AUTHOR]

A HPLC method based on matrix solid-phase dispersion (MSPD) was developed for simultaneous determination of fucoxanthin, lutein and astaxanthin in different microalgae. First, the powder of microalgae was blended with C8 adsorbent. Then the SPE column made from the microalgal matrix/sorbent (1:2) was eluted with 4 mL methanol (containing 0.1% BHT). The eluent was analyzed by HPLC. A C8 column and acetonitrile (ACN)/H2O as the mobile phase were used. The coefficient (R2) of each calibration curve was higher than 0.998. Limits of detection (LODs) and limits of quantification (LOQs) for each carotenoid were 0.30 µg g−1 and 1.00 µg g−1, respectively. The recovery at three concentration levels ranged from 69.1 to 106.5%, and the RSDs were lower than 5%. As a new sample preparation method for microalgal analysis, the MSPD procedure was optimized, validated and compared with conventional methods including ultrasonic and ice-bath extraction. The MSPD–HPLC method was accurate and reproducible. It was suitable for the quantitative determination of carotenoids in microalgae. [ABSTRACT FROM AUTHOR]

Fatty acid biomarkers of the marine microalga Isochrysis zhangjiangensis in response to nitrogen depletion were identified by multivariate statistical analysis. Seven fatty acids (C16:0, C18:1n9, C18:4n3, C18:3n3, C18:5n3, C22:6n3, and C16:1n7) were selected and identified as potential biomarkers, among which C18:1n9 and C18:4n3 were enriched in the neutral lipids and glycolipids, respectively. Due to significant changes and specific distributions in different types of lipids, C18:1n9 and C18:4n3 were identified as biomarkers to quantify neutral lipid content. C18:1n9 was positively related with neutral lipid content, while C18:4n3 was negatively related with neutral lipid content. The correlation coefficients of C18:1n9 and C18:4n3 content in total fatty acids and neutral lipid content were 0.9960 and 0.9787, respectively. The good agreement between the neutral lipids content and fatty acid biomarkers content in total fatty acids indicates that neutral lipids can be quantified by specific fatty acids. Using fatty acid biomarkers to quantify neutral lipids requires much less sample analyzed by gas chromatography, which is a universal method, plus the simplicity of operation compared with conventional methods. The striking feature of the approach is individual fatty acid to represent the type of lipids. Therefore, applying fatty acid biomarkers to identify specific type of lipids promises to maximize lipid-related information and can be used to make further discoveries related to lipid metabolism. [ABSTRACT FROM AUTHOR]

Microalgal starch is a potential feedstock for biofuel production. Nutrient stress is widely used to stimulate starch accumulation in microalgae. Cell growth and starch accumulation in the marine green microalga Tetraselmis subcordiformis were evaluated under extracellular phosphorus deprivation with initial cell densities (ICD) of 1.5, 3.0, 6.0, and 9.0 × 10 cells mL. The intracellular stored phosphorus supported cell growth when extracellular phosphorus was absent. The maximum starch content of 44.1 % was achieved in the lowest ICD culture, while the maximum biomass productivity of 0.71 g L day, starch concentration of 1.6 g L, and starch productivity of 0.30 g L day were all obtained in the culture with the ICD of 3.0 × 10 cells mL. Appropriate ICD could be used to regulate the intracellular phosphorus concentration and maintain adequate photosynthetic activity to achieve the highest starch productivity, along with biomass and starch concentration. The recovery of phosphorus-deprived T. subcordiformis in medium containing 0.5, 1.0, or 6.0 mM KHPO was also tested. Cell growth and starch accumulation ability could be recovered completely. A phosphorus pool in T. subcordiformis was shown to manipulate its metabolic activity under different environmental phosphorus availability. Though lower starch productivity and starch content were achieved under phosphorus deprivation compared with nitrogen- or sulfur-deprived conditions, the higher biomass and starch concentration make T. subcordiformis a good candidate for biomass and starch production under extracellular phosphorus deprivation. [ABSTRACT FROM AUTHOR]

Isochrysis zhangjiangensis is widely used in the marine aquaculture as larval feed, especially for filter feeding cultures, as well as a good candidate for biofuels. However, the optimal cultivation temperature for I. zhangjiangensis is below 30 °C and this stain is seriously affected by high temperature, which causes the limited application during the summer. I. zhangjiangensis IM130005 is a strain generated by atmospheric and room temperature plasmas with relative higher growth rate and lipid production than the wide strain (WT), with the ability to tolerate several hours' high temperature during the outdoor cultivation. Here, a detailed comparison was performed by continuous monitoring growth, chlorophyll fluorescence and fatty acid profile between IM13005 and WT under a mimic temperature shock to the summer outdoor cultivation. Based on a nearly 20% increase of total fatty acid in IM13005, which was majorly contributed by saturated or monounsaturated FAs in form of neutral lipids, within 5 h under the heat shock, the fatty acids and lipids synthesis variation were postulated as the physiological reason for the high temperature tolerance. [ABSTRACT FROM AUTHOR]