A Comprehensive Study of Techniques to Optimize the Extraction of Lipids from the Autotrophic Strain of the Microalgae Chlorella vulgaris

Microalgae represent a promising source of triglycerides and free fatty acids, synthesized in the form of lipids, for use in renewable fuels and chemicals. One challenge is the ability to efficiently recover the lipids from within the microalgae cell. Although various techniques have been studied individually, a comprehensive study of extraction techniques using consistent experimental and analytical methodology is missing. This study aims to provide this unifying comparison using the common microalgae strain Chlorella vulgaris. The factors that were surveyed and then optimized to achieve maximum extraction efficiency included the solvent type; mechanical pre-treatment using a ball mill at a variety of grinding speeds; microalgae-to-solvent ratio; extraction facilitated by microwave; extraction facilitated by sonication; extraction facilitated using increased temperature; and extraction facilitated by in situ transesterification to convert the lipids into esters prior to extraction. The optimum conditions determined during these studies were utilizing methanol as the solvent, with ball mill pretreatment at a grinding speed of 500 rpm, and a 1:9 microalgae to solvent ratio. When used in combination with microwave-assisted extraction at a temperature of 140 °C, approximately 24 wt% of the initial lipids were recovered. Recoveries of over 70 wt% were obtained without a microwave at extraction temperatures of over 200 °C.

Effect of Whey Protein Purity on the Characteristics of Algae Oil-Loaded Encapsulates Obtained by Electrospraying Assisted by Pressurized Gas

In this paper, the effect of protein purity in three different whey protein grades on the characteristics of algae oil encapsulates obtained via room-temperature electrospraying assisted by pressurized gas (EAPG) encapsulation process was studied. Three different commercial grades of whey protein purity were evaluated, namely 35, 80, and 90 wt.%. Oil nanodroplets with an average size of 600 nm were homogeneously entrapped into whey protein microparticles 3 µm in size. However, the sphericity and the surface smoothness of the microparticles increased by increasing the protein purity in the grades of whey protein studied. The porosity of the microparticles was also dependent on protein purity as determined by nitrogen adsorption-desorption isotherms, being smaller for larger contents of protein. Interestingly, the lowest extractable oil was obtained with WP35, probably due to the high content of lactose. The peroxide values confirmed the superior protective effect of the protein, obtaining the smallest peroxide value for WP90, a result that is consistent with its reduced porosity and with its lower permeability to oxygen, as confirmed by the fluorescence decay-oxygen consumption method. The accelerated stability assay against oxidation confirmed the higher protection of the WP80 and WP90. In addition, the increased content in protein implied a higher thermal stability according to the thermogravimetric analysis. These results further confirm the importance of the adequate selection of the composition of wall materials together with the encapsulation method.

Oxidized PUFAs Increase Susceptibility of Mice to Salmonella Infection by Diminishing Host's Innate Immune Responses

Dietary ω-3 PUFAs are highly prone to oxidation, and this may potentially limit their application in the health-promoting field. Here, we sought to investigate whether and how oxidized PUFAs modulate the susceptibility of mice to Salmonella typhimurium (S. Tm) infection. Algae oil (AO) and oxidized algae oil (ox-AO) were administered to the C57BL/6 mice prior to S. Tm infection. Compared to the S. Tm group, ox-AO increased bacterial burden in systemic and intestinal tissues, downregulated host anti-infection responses, and developed worse colitis. In macrophages, ox-AO decreased both phagocytosis of S. Tm and clearance of intracellular bacteria and dampened the activation of mitogen-activated protein kinase (MAPK), NF-κB, and autophagy pathways. Furthermore, ox-AO diminished LPS-induced inflammatory cytokine production and S. Tm induced NLRC4 inflammasome activation. This study reveals that oxidized PUFAs may contribute to the development of enteric infections and regular monitoring of the oxidation status in commercial PUFA supplements to prevent their potential adverse impact on human health.

Partial Substitution of Fish Oil with Microalgae (Schizochytrium sp.) Can Improve Growth Performance, Nonspecific Immunity and Disease Resistance in Rainbow Trout, Oncorhynchus mykiss

The price of fish oil has reached a historical peak due to a consistent downward production trend, and therefore, the search for sustainable alternative sources has received great attention. This research was conducted to evaluate dietary micro-algae, Schizochytrium sp. (SC) as fish oil (FO) replacer in rainbow trout, Oncorhynchus mykiss. In the first trial, apparent digestibility coefficient (ADC) was 92.4% for dry matter, 91.4% for crude protein, and 94.2% for crude lipid in rainbow trout. In the second trial, six diets were formulated to replace FO at 0% (CON), 20% (T20), 40% (T40), 60% (T60), 80% (T80), and 100% (T100) with SC in the rainbow trout (3.0 ± 0.4 g, mean ± SD) diet. After eight weeks’ feeding trial, weight gain (WG), specific growth rate (SGR), and feed efficiency (FE) of fish fed the T20 diet were significantly higher than those of fish fed other diets (p < 0.05). However, there were no significant differences in these parameters among those of fish fed CON, T40, T60, and T80 diets. Lysozyme activity of fish fed the T20 diet was significantly higher than those of fish fed other experimental diets (p < 0.05). After 10 days of disease challenge testing with pathogenic bacteria (Lactococcus garvieae 1 × 108 CFU/mL), the cumulative survival rate of fish fed the T20 diet was significantly higher than those of fish fed the CON, T80, and T100 diets. Therefore, these results suggest dietary microalgae SC is well-digested and could replace up to 80% of fish oil in the diet of rainbow trout without negative effects on growth and immune responses.

Synthesis and Characterization of Polyurethanes from Residual Palm Oil with High Poly-Unsaturated Fatty Acid Oils as Additive

In the effort to produce renewable and biodegradable polymers, more studies are being undertaken to explore environmentally friendly sources to replace petroleum-based sources. The oil palm industry is not only the biggest vegetable-oil producer from crops but also one the biggest producers of residual oil that cannot be used for edible purposes due to its low quality. In this paper the development of biopolymers from residual palm oil, residual palm oil with 10% jatropha oil, and residual palm oil with 10% algae oil as additives were explored. Polyols from the different oils were prepared by epoxydation with peroxyacetic acid and alcoholysis under the same conditions and further reacted with poly isocyanate to form polyurethanes. Epoxidized oils, polyols and polyurethanes were analyzed by different techniques such as TGA, DSC, DMA, FTIR and H-NMR. Overall, although the IV of algae oil is slightly higher than that of jatropha oil, the usage of algae oil as additive into the residual palm oil was shown to significantly increase the hard segments and thermal stability of the bio polyurethane compared to the polymer with jatropha oil. Furthermore, when algae oil was mixed with the residual palm oil, it was possible to identify phosphate groups in the polyol which might enhance the fire-retardant properties of the final biopolymer.

Addition of Olive Leaf Extract to a Mixture of Algae and Extra Virgin Olive Oils Decreases Fatty Acid Oxidation and Synergically Attenuates Age-Induced Hypertension, Sarcopenia and Insulin Resistance in Rats

Olive-derived products, such as virgin olive oil (EVOO) and/or olive leaf extracts (OLE), exert anti-inflammatory, insulin-sensitizing and antihypertensive properties and may be useful for stabilizing omega 3 fatty acids (n-3 PUFA) due to their high content in antioxidant compounds. In this study, the addition of OLE 4:0.15 (w/w) to a mixture of algae oil (AO) rich in n-3 PUFA and EVOO (25:75, w/w) prevents peroxides formation after 12 months of storage at 30 °C. Furthermore, the treatment with the oil mixture (2.5 mL/Kg) and OLE (100 mg/Kg) to 24 month old Wistar rats for 21 days improved the lipid profile, increased the HOMA-IR and decreased the serum levels of miRNAs 21 and 146a. Treatment with this new nutraceutical also prevented age-induced insulin resistance in the liver, gastrocnemius and visceral adipose tissue by decreasing the mRNA levels of inflammatory and oxidative stress markers. Oil mixture + OLE also attenuated the age-induced alterations in vascular function and prevented muscle loss by decreasing the expression of sarcopenia-related markers. In conclusion, treatment with a new nutraceutical based on a mixture of EVOO, AO and OLE is a useful strategy for improving the stability of n-3 PUFA in the final product and to attenuate the cardiometabolic and muscular disorders associated with aging.

Quantitation of Oxylipins in Fish and Algae Oil Supplements Using Optimized Hydrolysis Procedures and Ultra-High Performance Liquid Chromatography Coupled to Tandem Mass-Spectrometry

Fish and algae oil supplements are enriched with eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), which are precursors to oxidized fatty acids, known as oxylipins. Here, we optimized a base hydrolysis method for measuring oxylipins in oil with ultrahigh-performance liquid chromatography coupled to tandem mass-spectrometry (UPLC-MS/MS) and quantified them in fish and algae oil supplements. Hydrolysis of 2 μL of oil with sodium carbonate resulted in greater oxylipin concentrations and minimal matrix effects, compared to higher oil volumes (10, 20, and 30 μL). Oxylipin yield was higher when oil was hydrolyzed in methanol containing 0.1% acetic acid and 0.1% butylated hydroxytoluene, compared to no methanol, and using sodium hydroxide versus sodium carbonate. Oxylipins extracted from 2 μL of oil using sodium hydroxide in solvent showed that EPA-derived oxylipins were most abundant in fish oil (84-87%), whereas DHA-oxylipins were abundant in algae oil (83%). This study shows that fish and algae oils are direct sources of EPA- and DHA-derived oxylipins.

Nanodroplets of Docosahexaenoic Acid-Enriched Algae Oil Encapsulated within Microparticles of Hydrocolloids by Emulsion Electrospraying Assisted by Pressurized Gas

Long chain polyunsaturated omega-3 fatty acids (PUFAs), namely eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), are important functional ingredients due to their well-documented health benefits, but highly susceptible to oxidation. One of the most promising approaches to preserve bioactives is their encapsulation within protective matrices. In this paper, an innovative high throughput encapsulation technique termed as emulsion electrospraying assisted by pressurized gas (EAPG) was used to encapsulate at room temperature nanodroplets of algae oil into two food hydrocolloids, whey protein concentrate and maltodextrin. Spherical encapsulating particles with sizes around 5 µm were obtained, where the oil was homogeneously distributed in nanometric cavities with sizes below 300 nm. Peroxide values under 5 meq/kg, demonstrated that the oil did not suffer from oxidation during the encapsulation process carried out at room temperature. An accelerated stability assay against oxidation under strong UV light was performed to check the protective capacity of the different encapsulating materials. While particles made from whey protein concentrate showed good oxidative stability, particles made from maltodextrin were more susceptible to secondary oxidation, as determined by a methodology put forward in this study based on ATR-FTIR spectroscopy. Further organoleptic testing performed with the encapsulates in a model food product, i.e., milk powder, suggested that the lowest organoleptic impact was seen for the encapsulates made from whey protein concentrate. The obtained results demonstrate the potential of the EAPG technology using whey protein concentrate as the encapsulating matrix, for the stabilization of sensitive bioactive compounds.

Algae Oil Treatment Protects Retinal Ganglion Cells (RGCs) via ERK Signaling Pathway in Experimental Optic Nerve Ischemia

Background: We investigated the therapeutic effects and related mechanisms of algae oil (ALG) to protect retinal ganglion cells (RGCs) in a rat model of anterior ischemic optic neuropathy (rAION). Methods: Rats were daily gavaged with ALG after rAION induction for seven days. The therapeutic effects of ALG on rAION were evaluated using flash visual evoked potentials (FVEPs), retrograde labeling of RGCs, TUNEL assay of the retina, and ED1 staining of optic nerves (ONs). The levels of inducible nitric oxide synthase (iNOS), IL-1β, TNF-α, Cl-caspase-3, ciliary neurotrophic factor (CNTF), and p-ERK were analyzed by using western blots. Results: Protection of visual function in FVEPs amplitude was noted, with a better preservation of the P1–N2 amplitude in the ALG-treated group (p = 0.032) than in the rAION group. The density of RGCs was 2.4-fold higher in the ALG-treated group compared to that in the rAION group (p < 0.0001). The number of ED1-positive cells in ONs was significantly reduced 4.1-fold in the ALG-treated group compared to those in the rAION group (p = 0.029). The number of apoptotic RGCs was 3.2-fold lower in number in the ALG-treated group (p = 0.001) than that in the rAION group. The ALG treatment inhibited ERK activation to reduce the levels of iNOS, IL-1β, TNF-α, and Cl-caspase-3 and to increase the level of CNTF in the rAION model. Conclusion: The treatment with ALG after rAION induction inhibits ERK activation to provide both anti-inflammatory and antiapoptotic effects in rAION.

Emulsification and oxidation stabilities of DAG-rich algae oil-in-water emulsions prepared with the selected emulsifiers

BACKGROUND

Diacylglycerol (DAG) reduces body weight, suppresses body fat accumulation, and lowers the blood lipid concentration, and docosahexaenoic acid (DHA) can reduce the risk of occurrence of coronary artery diseases.

RESULTS

DAG-rich algae oil with a high DHA content (55.9%) was synthesized via the lipase-catalyzed glycerolysis of algae oil, which consisted of triacylglycerol (43.9 mol%), DAG (40.9 mol%), and monoacylglycerol (15.2 mol%). The DAG-rich algae oil-in-water emulsions were prepared using three emulsifiers [whey protein concentrate (WPC), Tween80, and Tween80 + Span80]. The WPC-emulsion formed a thicker serum layer (6.67% at day 51) and larger oil droplets (d₃₂ , 0.37 μm at day 28) than the Tween80- and Tween80 + Span80-emulsions (3.33-4.17%; 0.26 μm), and an upper cream layer with excess oil droplets was observed in only the WPC-emulsion, indicating that WPC-emulsion possesses the lowest emulsification stability. The hydroperoxide value and reduction rate of the DHA content were higher in the WPC-emulsions than in the Tween80- and Tween80 + Span80-emulsions during storage, which suggested that the WPC-emulsion had the lowest oxidation stability.

CONCLUSION

The DAG-rich algae oil-in-water emulsion prepared with suitable emulsifiers, such as non-ionic emulsifiers, would have excellent emulsification and oxidative stabilities and provides a health benefit for special purposes in the food processing industry. © 2019 Society of Chemical Industry.

Increased Cellular Uptake of Polyunsaturated Fatty Acids and Phytosterols from Natural Micellar Oil

The transport of hydrophobic compounds to recipient cells is a critical step in nutrient supplementation. Here, we tested the effect of phospholipid-based emulsification on the uptake of hydrophobic compounds into various tissue culture cell lines. In particular, the uptake of ω-3 fatty acids from micellar or nonmicellar algae oil into cell models for enterocytes, epithelial cells, and adipocytes was tested. Micellization of algae oil did not result in adverse effects on cell viability in the target cells. In general, both micellar and nonmicellar oil increased intracellular docosahexaenoic acid (DHA) levels. However, micellar oil was more effective in terms of augmenting the intracellular levels of total polyunsaturated fatty acids (PUFAs) than nonmicellar oil. These effects were rather conserved throughout the cells tested, indicating that fatty acids from micellar oils are enriched by mechanisms independent of lipases or lipid transporters. Importantly, the positive effect of emulsification was not restricted to the uptake of fatty acids. Instead, the uptake of phytosterols from phytogenic oils into target cells also increased after micellization. Taken together, phospholipid-based emulsification is a straightforward, effective, and safe approach to delivering hydrophobic nutrients, such as fatty acids or phytosterols, to a variety of cell types in vitro. It is proposed that this method of emulsification is suitable for the effective supplementation of numerous hydrophobic nutrients.

ω-3 PUFAs Alleviate High-Fat Diet-Induced Circadian Intestinal Microbes Dysbiosis

SCOPE

Published data support that fish oil and algae oil rich in ω-3 polyunsaturated fatty acids (PUFAs) protect against hyperlipidemia in mice. This study is aimed to explore the effects of fish oil and algae oil on high-fat diet (HFD) induced circadian intestinal microbes dysregulation.

METHODS AND RESULTS

Male C57BL/6 mice are randomly divided into four groups, which are fed a normal chow diet (CON), a HFD, a HFD supplemented with fish oil (FO), and a HFD supplemented with algae oil (AO), respectively, for 12 weeks. At the end of the experiment, mice are sacrificed at 12 h intervals with the first one at zeitgeber time 0 (ZT0) and the second at zeitgeber time 12 (ZT12). FO and AO groups ameliorate diet-induced hyperlipidemia. The relative abundance of certain genera is improved in FO and AO groups according to 16S rRNA gene sequencing. The short-chain fatty acids (SCFAs) producing bacteria Butyricimonas and some of the genera in the Lachnospiraceae recover to the normal circadian rhythm in both FO and AO groups.

CONCLUSION

The data show that FO and AO alleviate circadian gut microbiota dysregulation in mice caused by HFD, and support the further investigation of ω-3 PUFAs as a dietary intervention strategy for the prevention of hyperlipidemia.

DHA rich algae oil delivered by O/W or gelled emulsions: strategies to increase its bioaccessibility

BACKGROUND

The bioaccessibility of bioactive compounds for functional food deserves evaluation. An in vitro gastrointestinal digestion model was applied to provide information about the extent of lipid hydrolysis, oxidative stability and bioaccessibility of algae oil (42% of docosahexaenoic acid; DHA), comparing three lipid delivery systems: bulk oil, soy protein stabilized O/W emulsion and carrageenan gelled emulsion.

RESULTS

Lipid digestion kinetics was slightly influenced by the delivery systems. Nevertheless, at the end of intestinal digestion, lipolysis in the three samples ranged between 49% and 52%, showing a partial oil digestion. Lipid oxidation, measured by malondialdehyde, was significantly lower (P < 0.01) in both emulsified oils after intestinal digestion compared to the bulk oil. Bioaccessibility of DHA was 58%, 71% and 84% for bulk oil, O/W emulsion and gelled emulsion, respectively.

CONCLUSION

These results suggest that both emulsified delivery systems used in the present study enhanced the solubilization of free fatty acids, in particular omega-3 fatty acids, and therefore their potential intestinal absorption. © 2018 Society of Chemical Industry.

Preparation and Evaluation of Release Formulation of γ-Oryzanol/Algae Oil Self-Emulsified with Alginate Beads

Self-emulsion improves solubility and bioavailability for γ-oryzanol/algae oil, and alginate beads can be used as controlled release carriers. In this study, self-emulsified alginate beads (SEABs) were prepared with different weight ratios of self-emulsion treatment (5%, 10%, 15%, 20%, and 30%) with alginate. We found that the microstructure with a surfactant of SEABs had a different appearance with alginate-based beads. The encapsulation of γ-oryzanol corresponded with the self-emulsion/alginate ratio, which was 98.93~60.20% with a different formulation of SEABs. During in vitro release, SEABs had the gastric protection of γ-oryzanol/algae oil, because γ-oryzanol and emulsion were not released in the simulated stomach fluid. When the SEABs were transferred to a simulation of the small intestine, they quickly began to swell and dissolve, releasing a higher content of the emulsion. We observed that the emulsion that formed had a bimodal distribution in the simulated intestinal fluid as a result of the hydrogel and emulsion droplets, leading to the formation of large aggregates. These results suggested that γ-oryzanol encapsulation within alginate beads via emulsification combined with gelation can serve as an effective controlled delivery system.

Storage stability of egg sticks fortified with omega-3 fatty acids

BACKGROUND

Egg sticks fortified with omega-3 polyunsaturated fatty acids (ω-3 PUFAs) were developed by replacing egg yolk with salmon, algae, and flax oils. Egg sticks were cooked before analysis. Quality indicators for storage stability under different packaging and temperature were determined throughout a 28-day storage. Egg sticks were vacuum and non-vacuum packed. Further, both packaging treatments were divided into two storage temperatures of 4 and 10 °C. Quality indicators were determined every 7 days, including pH, syneresis, texture, color, microbial growth, proximate composition, fatty acid profile, and lipid oxidation.

RESULTS

Vacuum-packed egg sticks stored at 4 °C had slower degradation over time than all other treatments; however, they also had higher syneresis, harder texture, and higher anaerobic growth. Although vacuum packaging slowed lipid oxidation, it had limited effect on prevention of ω-3 PUFAs degradation; whereas refrigeration (4 °C) seemed to prevent degradation of ω-3 PUFAs better than it could slow lipid oxidation.

CONCLUSION

Based on the results, it can be concluded that both vacuum packaging and refrigeration at 4 °C decrease degradation of egg sticks developed in the present study during storage. Under these conditions, egg sticks may maintain stability for at least 21 days of storage. © 2017 Society of Chemical Industry.

Sex-Based Differences in Gut Microbiota Composition in Response to Tuna Oil and Algae Oil Supplementation in a D-galactose-Induced Aging Mouse Model

Our previous work indicated that a mixture of tuna oil and algae oil treatment in male mice effectively relieved D-galactose (D-gal)-induced aging and resulted in gut microbiota alterations, and that the best anti-aging effects were observed for a tuna oil to algae oil ratio of 1:2. However, the possibility of a sex-based difference in the anti-aging effect of the tuna oil and algae oil mixture or gut microbiota variation, has rarely been investigated. In this study, the anti-aging effect of an oil mixture (1:2) in male and female mice was measured, and oil treatment improved the learning and cognition of mice that were damaged by D-gal, increased the activities of anti-oxidative enzymes, and decreased the level of MDA, which acted as a hallmark of oxidative damage to lipids. Male mice showed better anti-aging effects than female mice with a specific oil mixture ratio, and the clinical drug donepezil showed a similar or better effect on aging alleviation than oil treatments in both sexes. On the other hand, the same oil treatment led to different gut microbiota composition alterations in male and female mice. Redundancy analysis (RDA) identified 31 and 30 key operational taxonomic units (OTUs) in the male and female mice, respectively, and only three of these OTUs overlapped. Moreover, the abundance of Lactobacillus and several probiotic-like butyric acid producers was higher in male mice than in female mice, whereas the abundance of some inflammation-related genera, such as Clostridium XlVa, was lower in male mice. In conclusion, this study indicated the sex-based differences related to the anti-aging effects of tuna oil and algae oil treatment are accompanied by sex-based differences in gut microbiota modulation.