The regulation of lipid biosynthesis is essential in photosynthetic eukaryotic cells. This regulation occurs during the direct synthesis of fatty acids and triacylglycerols (TAGs), as well as during other controlling processes in the main carbon metabolic pathway.
Results
In this study, the mRNA levels of Chlamydomonas citrate synthase (CrCIS) were found to decrease under nitrogen-limited conditions, which suggests suppressed gene expression. Gene silencing by RNA interference (RNAi) was conducted to determine whether CrCIS suppression affected the carbon flux in TAG biosynthesis. Results showed that the TAG level increased by 169.5%, whereas the CrCIS activities in the corresponding transgenic algae decreased by 16.7% to 37.7%. Moreover, the decrease in CrCIS expression led to the increased expression of TAG biosynthesis-related genes, such as acyl-CoA:diacylglycerol acyltransferase and phosphatidate phosphatase. Conversely, overexpression of CrCIS gene decreased the TAG level by 45% but increased CrCIS activity by 209% to 266% in transgenic algae.
Conclusions
The regulation of CrCIS gene can indirectly control the lipid content of algal cells. Our findings propose that increasing oil by suppressing CrCIS expression in microalgae is feasible.
Microbial oils are among the most attractive alternative feedstocks for biodiesel production. In this study, a newly isolated yeast strain, AM113 of Papiliotrema laurentii, was identified as a potential lipid producer, which could accumulate a large amount of intracellular lipids from hydrolysates of inulin. P. laurentii AM113 was able to produce 54.6% (w/w) of intracellular oil in its cells and 18.2 g/l of dry cell mass in a fed-batch fermentation. The yields of lipid and biomass were 0.14 and 0.25 g per gram of consumed sugar, respectively. The lipid productivity was 0.092 g of oil per hour. Compositions of the fatty acids produced were C14:0 (0.9%), C16:0 (10.8%), C16:1 (9.7%), C18:0 (6.5%), C18:1 (60.3%), and C18:2 (11.8%). Biodiesel obtained from the extracted lipids could be burnt well. This study not only provides a promising candidate for single cell oil production, but will also probably facilitate more efficient biodiesel production. 相似文献
In the study, epoxidation of dodecanol monomaleate, hexadecanol monomaleate, and octadecanol monomaleate were carried out using [π-C5H5N(CH2)15CH3]3PO4(WO3)4 as phase-transfer catalyst with 30% hydrogen peroxide as oxidant. The experimental results showed that [π-C5H5N(CH2)15CH3]3PO4(WO3)4 had excellent catalytic effect on translating C=C double-bond into an epoxy group and had a good yield rate. The synthesized epoxides of decanol monomaleate, hexadecanol monomaleate, and octadecanol monomaleate have enormous potential application in organic synthesis, and they could be readily transformed into various synthetically useful intermediates or final products in many fields of chemistry. 相似文献
Macrophages are phagocytic cells which are involved in the non-specific immune defense. Lipid uptake and storage behavior of macrophages also play a key role in the development of atherosclerotic lesions within walls of blood vessels. The allocation of exogenous lipids such as fatty acids in the blood stream dictates the accumulation and quantity of lipids within macrophages. In case of an overexposure, macrophages transform into foam cells because of the large amount of lipid droplets in the cytoplasm. Raman micro-spectroscopy is a powerful tool for studying single cells due to the combination of microscopic imaging with spectral information. With a spatial resolution restricted by the diffraction limit, it is possible to visualize lipid droplets within macrophages. With stable isotopic labeling of fatty acids with deuterium, the uptake and storage of exogenously provided fatty acids can be investigated. In this study, we present the results of time-dependent Raman spectroscopic imaging of single THP-1 macrophages incubated with deuterated arachidonic acid. The polyunsaturated fatty acid plays an important role in the cellular signaling pathway as being the precursor of icosanoids. We show that arachidonic acid is stored in lipid droplets but foam cell formation is less pronounced as with other fatty acids. The storage efficiency in lipid droplets is lower than in cells incubated with deuterated palmitic acid. We validate our results with gas chromatography and gain information on the relative content of arachidonic acid and its metabolites in treated macrophages. These analyses also provide evidence that significant amounts of the intracellular arachidonic acid is elongated to adrenic acid but is not metabolized any further. The co-supplementation of deuterated arachidonic acid and deuterated palmitic acid leads to a non-homogenous storage pattern in lipid droplets within single cells. Figure a
Nanopores based on α-hemolysin and MspA represent attractive sensing platforms due to easy production and operation with relatively low background noise. Such characteristics make them highly favorable for sequencing nucleic acids. Artificial lipid bilayer membranes, also referred to as black lipid membranes, in conjunction with membrane nanopores, can be applied to both the detection and highly efficient sequencing of DNA on a single-molecule level. However, the inherently weak physical properties of the membrane have impeded progress in these areas. Current issues impeding the ultimate recognition of the artificial lipid bilayer as a viable platform for detection and sequencing of DNA include membrane stability, lifespan, and automation. This review (with 105 references) highlights attempts to improve the attributes of the artificial lipid bilayer membrane starting with an overview on the present state and limitations. The first main section covers lipid bilayer membranes (BLM) in general. The following section reviews the various kinds of lipid bilayer membrane platforms with subsections on polymer membranes, solid-supported membranes, hydrogel-encapsulated membranes, shippable and storable membrane platforms, and droplet interface bilayers. A further section covers engineered biological nanopore sensor applications using BLMs with subsections offering a comparative view of different DNA sequencing methods, a detailed look at DNA Sequencing by synthesis using alpha-hemolysin nanopores, sequencing by synthesis using the MspA nanopore and quadromer map, and on limitations of sequencing based on synthesis technology. We present an outlook at the end that discusses current research trends on single-molecule sequencing to highlight the significance of this technology and its potential in the medical and environmental fields.
Graphical abstract Sequencing by Synthesis, a novel method of sequencing DNA, uses the αHL biological nanopore and the artificial lipid bilayer membrane platform. Polymer tags attached to nucleotides bind to the polymerase-primer–template complex and are characterized by the nanopore upon release.
The objective of this research was to investigate the kinetics of lipid production by Yarrowia lipolytica SKY7 in the crude glycerol-supplemented media with and without the control of pH. Lipid and citric acid production were improved with the pH control condition. There was no significant difference observed in the biomass concentration with or without the pH control. In the pH-controlled experiments, the biomass and lipid concentration reached 18 and 7.78 g/L, (45.5% w/w), respectively, with lipid yield (Yp/s) of 0.179 g/g at 60 h of fermentation. The lipid production was directly correlated with growth and the process was defined as growth associated. After 60 h of fermentation, the lipid degradation was noticed in the pH-controlled reactor whereas it occurred after 84 h in the pH-uncontrolled reactor. Apart from lipid, citric acid was produced as the major extracellular product in both fermentations but the much lower concentration in uncontrolled pH. Based on the experimental results, it is evident that controlling the pH will enhance the lipid production by 15% compared to pH-uncontrolled fermentation. 相似文献
The ability to control the charge state and ionization efficiency of lipids and hydrocarbons by means of in-source Paternò-Büchi functionalization in nano-electrospray ionization mass spectrometry experiments is investigated. Ultraviolet light irradiation of acetylpyridine filled nano-electrospray emitter tips, containing unsaturated analytes, generates protonated lipid and hydrocarbon ions. Comparison of reaction yields and fragment ion abundances of functionalized unsaturated fatty acids indicate that acetylpyridine Paternò-Büchi functionalization allows to readily detect fatty acids and determine double bond positions, but fragmentation efficiency and reactivity depend on double bond position and varies between different acetylpyridine isomers. Results for methyl oleate and olefins suggest that fragment ion abundances of unsaturated compounds depend on interactions between acetylpyridine and nearby functional groups. Paternò-Büchi functionalization with acetylpyridine was used to detect and assign double bond positions of mono- and polyunsaturated fatty acid, cholesterol ester, triglyceride, and hydrocarbon standards with ion abundances that are up to 631 times higher than abundances of the same compounds prior Paternò-Büchi reaction. To demonstrate the scope and analytical robustness of the newly developed method, free fatty acids in mouse brain as well as male Schistosoma mansoni extracts and hydrocarbons in an olefin mixture are investigated. For this complex set of analytes, charging and charge switching using acetylpyridine Paternò-Büchi functionalization enable double bond position assignment and relative quantification in positive ion mode.
A bioassay-guided purification of the methanolic extract of Withania somnifera fruits yielded novel withanamides A-I (1-9) and withanolides (10-13). Among the withanolides, compound 10 is novel. The structures of these compounds were determined by using FABMS, HRFABMS, 1D and 2D NMR spectral and chemical methods. The withanamides possess novel chemical structures and consisted of serotonin, glucose and long-chain hydroxyl fatty acid moieties. The stereochemistry of the hydroxyl group in the long-chain fatty acid moiety in compound 1 was determined by the modified Mosher's ester method. Compounds 1-13 were tested for their ability to inhibit lipid peroxidation in a model system using large unilamellar vesicles. Withanamides 1-5 and 9 inhibited lipid peroxidation by 98, 93, 79, 94, 81 and 86%, respectively, at 1 μg/mL. However, compounds 6-8 inhibited the lipid peroxidation by 85, 82 and 90%, respectively, at 0.5 μg/mL. Withanolides 10-13 were also tested and only compound 12 inhibited the lipid peroxidation by 82% at 10 μg/mL. To evaluate the structure activity relationships of withanamides A-I, compounds 14-16 were purchased and their lipid peroxidation activity determined as in the case of compounds 1-9. Commercial antioxidants, butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT) and tert-butylhydroquinone (TBHQ), were also tested in this assay at 1 μg/mL and showed 80, 81 and 85% of inhibition, respectively. Our results suggest that the potent antioxidant activity exhibited by novel withanamides is probably due to the hydroxylated long-chain acyl group. This is the first report of withanamides, unique serotonin conjugates, from W. somnifera fruits. 相似文献
Entomopathogenic fungi are referred to as potential candidates as insect pest control agents. The objective of the study was to identify fatty acids and amino acids from Conidiobolus coronatus cultured on two different media. Each medium was extracted with ethyl acetate and its mixtures with isopropanol, acetonitrile and methanol. Analyses of fatty acids and amino acids of entomopathogenic fungus C. coronatus were performed by means of gas chromatography coupled with mass spectrometry. The analysis showed that the fungus C. coronatus produces the following groups of compounds: fatty acids and amino acids; α- and β-glucopyranose were also identified. The identified fatty acids included 12–20, 22 and 24 carbon atoms per chain. The highest content of fatty acids was detected in a mycelium sample cultured in a liquid minimal medium extracted with ethyl acetate. The lowest content of these organic compounds was identified in mycelium cultured in a liquid nutrient-rich medium extracted with ethyl acetate–methanol mixture. Fatty acids were found to account for 62.0 mass % to 94.4 mass % of all organic compounds in the analyzed mycelia. C18:1 acids were detected in the highest amounts when ethyl acetate was used as the extracting agent. The identified amino acids accounted for 4 mass % to 21 mass % of all organic compounds. Upon extraction of C. coronatus mycelium samples with the ethyl acetate—methanol mixture, two anomeric forms of glucose were also identified. An analysis of the studied material confirmed, that the entomopathogenic fungus C. coronatus is a very rich source of organic compounds, which might encourage its further research so as to identify an even larger number of compounds being produced by this species. 相似文献
The lipopolysaccharides (LPSs) have been isolated from two blue-green algae,Oscillatoria hilderbrandtii andNostoc sp. by the method of phenol-water extraction. The LPSs contain polysaccharide and lipid components. The polysaccharide fraction fromO. hildebrandtii consists predominantly of 1,3-bound rhamnose residues with a substituent in the second position. The rhamnose residues in the polysaccharide fraction ofNostoc are connected by 1,3- and 1,2-glycosidic bonds. The lipid components of the LPSs fromO. hilderbrandtii andNostoc consist of palmitic and steric acids, with glucosamine and glucose. 相似文献
