Microalgal polysaccharides have been reported in many studies due to their uniqueness, biocompatibility, and high value, and
Rhodosorus
sp. SCSIO-45730 was an excellent source of polysaccharides and ...β-glucans. However, the polysaccharides from the red unicellular alga
Rhodosorus
sp. SCSIO-45730 have barely been studied. In this work, hot water extraction of
Rhodosorus
sp. SCSIO-45730 polysaccharides (RSP) was optimized using response surface methodology (RSM) based on Box–Behnken design (BBD). The maximum RSP yield (9.29%) was achieved under the optimum extraction conditions: liquid–solid ratio of 50.00 mL g
−1
; extraction temperature of 84 °C; extraction time of 2 h; and extraction times of 5 times. The results of physicochemical characterization showed that RSP had high sulfate and uronic acid with content of 19.58% and 11.57%, respectively, rough layered structure, and mainly contained glucose, galactose, xylose, and galacturonic acid with mass percentages of 34.08%, 28.70%, 12.46%, and 12.10%. Furthermore, four kinds of antioxidant assays were carried out, and the results indicated that RSP had strong scavenging activities on ABTS and hydroxyl radical and moderate scavenging activities on DPPH and ferrous chelating ability. These results indicated that RSP showed potential as a promising source of antioxidants applied in food, pharmaceutical, and cosmetics industry.
The marine red microalga
can simultaneously synthesize long-chain polyunsaturated fatty acids, including eicosapentaenoic acid (C20:5, EPA) and arachidonic acid (C20:4, ARA). However, the ...distribution and synthesis pathways of EPA and ARA in
are not clearly understood. In this study,
CCALA 415 was cultured in nitrogen-replete and nitrogen-limited conditions. Fatty acid content determination, transcriptomic, and lipidomic analyses were used to investigate the synthesis of ARA and EPA. The results show that membrane lipids were the main components of lipids, while storage lipids were present in a small proportion in CCALA 415. Nitrogen limitation enhanced the synthesis of storage lipids and ω6 fatty acids while inhibiting the synthesis of membrane lipids and ω3 fatty acids. A total of 217 glycerolipid molecular species were identified, and the most abundant species included monogalactosyldiglyceride (C16:0/C20:5) (MGDG) and phosphatidylcholine (C16:0/C20:4) (PC). ARA was mainly distributed in PC, and EPA was mainly distributed in MGDG. Among all the fatty acid desaturases (FADs), the expressions of Δ5FAD, Δ6FAD, Δ9FAD, and Δ12FAD were up-regulated, whereas those of Δ15FAD and Δ17FAD were down-regulated. Based on these results, only a small proportion of EPA was synthesized through the ω3 pathway, while the majority of EPA was synthesized through the ω6 pathway. ARA synthesized in the ER was likely shuttled into the chloroplast by DAG and was converted into EPA by Δ17FAD.
A novel method using ethanol was proposed for extracting lipids from wet microalga Picochlorum sp. at room temperature and pressure. In this study, Central Composite design (CCD) was applied to ...investigate the optimum conditions of lipid extraction. The results revealed that the solvent to biomass ratio had the largest effect on lipid extraction efficiency, followed by extraction time and temperature. A high lipid extraction yield (33.04% of the dry weight) was obtained under the following extraction conditions: 5 mL solvents per gram of wet biomass for 37 min with gentle stirring at room temperature. The extraction yield was comparable to that obtained by the widely used Bligh-Dyer method. Furthermore, no significant differences in the distribution of lipid classes and fatty acid composition were observed according to different extraction methods. In conclusion, these results indicated that the proposed procedure using ethanol could extract lipids from wet biomass efficiently and had giant potential for lipid extraction at large scale.
Surface-capping agents play key roles in cellular uptake and biological activity of functional nanomaterials. In the present study, functionalized selenium nanoparticles (SeNPs) have been ...successfully synthesized using Polyporus rhinocerus water-soluble polysaccharide–protein complexes (PRW) as the capping agent during the reduction of selenium salts. The acquired monodisperse, spherical PRW-SeNPs presented desirable size distribution and stability in the solution. Moreover, PRW surface decoration significantly enhanced the cellular uptake of SeNPs via endocytosis. Exposure to PRW-SeNPs significantly inhibited the growth of A549 cells through induction of apoptosis and G2/M phase arrest (IC50 = 4.06 ± 0.25 μM) supported by an increase of sub-G1 and G2/M phase cell populations, DNA fragmentation, and chromatin condensation. Caspase-3/8 activation induced by PRW-SeNPs indicated that the activation of death receptors was the main cause of PRW-SeNP-induced apoptosis. Collectively, the results suggest that it is highly efficient to use PRW as a surface decorator of SeNPs to enhance cellular uptake and anticancer efficacy, and the PRW-SeNPs are potential chemopreventive agents for lung cancer therapy.
Lipid production is an important indicator for assessing microalgal species for biodiesel production. In this work, the effects of medium composition on lipid production by Scenedesmus sp. were ...investigated using the response surface methodology. The results of a Plackett-Burman design experiment revealed that NaHCO₃, NaH₂PO4·2H₂O and NaNO₃ were three factors significantly influencing lipid production, which were further optimized by a Box-Behnken design. The optimal medium was found to contain 3.07 g L⁻¹ NaHCO₃, 15.49 mg L⁻¹ NaH₂PO4·2H₂O and 803.21 mg L⁻¹ NaNO₃. Using the optimal conditions previously determined, the lipid production (304.02 mg·L⁻¹) increased 54.64% more than that using the initial medium, which agreed well with the predicted value 309.50 mg L⁻¹. Additionally, lipid analysis found that palmitic acid (C16:0) and oleic acid (C18:1) dominantly constituted the algal fatty acids (about 60% of the total fatty acids) and a much higher content of neutral lipid accounted for 82.32% of total lipids, which strongly proved that Scenedesmus sp. is a very promising feedstock for biodiesel production.
•A common newly isolated strain of Nannochloropsis gaditana was investigated.•The influence of cultivation period on growth and lipid properties were examined.•Most of the examined items linear ...changed with the cultivation period extension.•Lipid productivity revealed a growth cessation in 16days.•All of the biofuel properties satisfied the specifications of biodiesel standard.
This work reported for the first time the detailed impacts of cultivation period on growth dynamics and biochemical composition of a microalga strain Nannochloropsis gaditana 1049. The results shown either the biomass accumulation, lipid content, neutral lipid content, monounsaturated fatty acids composition or the favorable fatty acid profile of C16–C18 increased along with the cultivation period extension, but the lipid productivity displayed a decrease since cultured for 16days, with the highest value reached 289.51±16.34mgL−1d−1. Biodiesel properties of this microalga also changed with the cultivation period extension, with average unsaturated degree decreased from 1.24±0.03 to 0.59±0.02, cloud point increased from 3.39±0.40°C to 12.14±0.32°C, cetane number increased from 54.59±0.20 to 58.96±0.16 and iodine number reduced sharply from 105.15±2.24gI2/100g to 56.44±1.76gI2/100g, which all satisfied the specifications of biodiesel standard.
Microalgae oil is an optimal feedstock for nutraceutical, pharmaceutical and biodiesel production, but its high levels of chlorophyll limit its large-scale application. To date, few effective ...approaches have been developed to remove chlorophyll from microalgae oil. The main purpose of this study was to present a preprocessing method of algae oil feedstock (Scenedesmus) to remove chlorophyll by saponification. The results showed that 96% of chlorophyll in biomass was removed. High quality orange transparent oil could be extracted from the chlorophyll reduced biomass. Specifically, the proportion of neutral lipids and saturation levels of fatty acids increased, and the pigments composition became carotenoids-based. The critical parameters of chlorophyll reduced biodiesel conformed to the standards of the USA, China and EU. Sodium copper chlorophyllin could be prepared from the bleaching effluent. The results presented herein offer a useful pathway to improve the quality of microalgae oil and reduce the cost of microalgae biodiesel.
Phaeodactylum tricornutum
is a potential livestock for the combined production of eicosapentaenoic acid (EPA) and fucoxanthin. In this study, six marine diatom strains identified as
P. tricornutum
...were cultured and their total lipid, fatty acid composition and major photosynthetic pigments determined. It was found that the cell dry weight concentration and mean growth rate ranged between 0.24–0.36 g/L and 0.31–0.33/d, respectively. Among the strains, SCSIO771 presented the highest total lipid content, followed by SCSIO828, and the prominent fatty acids in all strains were C16:0, C16:1, C18:1, and C20:5 (EPA). Polyunsaturated fatty acids, including C16:2, C18:2, and EPA, comprised a significant proportion of the total fatty acids. EPA was markedly high in all strains, with the highest in SCSIO828 at 25.65% of total fatty acids. Fucoxanthin was the most abundant pigment in all strains, with the highest in SCSIO828 as well, at 5.50 mg/g. The collective results suggested that strain SCSIO828 could be considered a good candidate for the concurrent production of EPA and fucoxanthin.
Recently, a novel method using ethanol was proposed for extracting lipids from wet Picochlorum sp. at room temperature and pressure. In this study, the feasibility of the method was assessed in ...several microalgae species with high moisture (Chlorella sp. 442, Chlorella sp. 725, and Picochlorum sp. 802). The result revealed that high lipid extraction yields (approximately 30% of the dry weight) were obtained when using ethanol, which were comparable to those obtained by the Bligh–Dyer method. For each species, no significant differences in terms of the distribution of lipid classes and fatty acid composition were observed based on the different extraction methods. These results demonstrated that the proposed procedure could be applied in extracting lipids from wet microalgae successfully. After lipid extraction, algal cells were damaged exhibited by pits and gaps, but the cell disruption efficiency was lower than 30%, suggesting that lipids were mainly released through pits and gaps, followed by cell lysis. Additionally, for each species, the wet lipid-extracted algal residues contained high protein content, which could be a promising source of high-value byproducts.
In order to rapidly screen microalgae species as feedstocks for antioxidants, extracts were obtained from 16 microalgae strains (under 11 genera, 7 classes) using two methods: a one-step extraction ...with ethanol/water and a three-step fractionating procedure using hexane, ethylacetate, and water successively. Measuring the total phenol content (TPC), total carotenoid content (TCC), and antioxidant activity of the extracts, indicating TPC and TCC, played an important role in determining the antioxidant activity of the microalgae. A weighted scoring system was used to evaluate the antioxidant activity, and the scores of microalgal samples from two extraction methods were calculated using the same system. Among the investigated microalgae,
SCSIO-46781 had the highest antioxidant score, contributing to high TPC and TCC, followed by
SCSIO-44012,
sp. SCSIO-45224,
SCSIO-45120, and
sp. SCSIO-45006, respectively. Additionally, the above-mentioned five strains are currently being applied in commercial production, indicating this system could be effective not only for screening microalgal antioxidants, but also for screening microalgal species/strains with strong adaptation to environmental stress, which is a critical trait for their commercial cultivation.
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