Microalgae Oil Research Articles

Producing Designer Oils in Industrial Microalgae by Rational Modulation of Co-evolving Type-2 Diacylglycerol Acyltransferases

Microalgal oils, depending on their degree of unsaturation, can be utilized as either nutritional supplements or fuels; thus, a feedstock with genetically designed and tunable degree of unsaturation is desirable to maximize process efficiency and product versatility. Systematic profiling of ex vivo (in yeast), in vitro, and in vivo activities of type-2 diacylglycerol acyltransferases in Nannochloropsis oceanica (NoDGAT2s or NoDGTTs), via reverse genetics, revealed that NoDGAT2A prefers saturated fatty acids (SFAs), NoDGAT2D prefers monounsaturated fatty acids (MUFAs), and NoDGAT2C exhibits the strongest activity toward polyunsaturated fatty acids (PUFAs). As NoDGAT2A, 2C, and 2D originated from the green alga, red alga, and eukaryotic host ancestral participants of secondary endosymbiosis, respectively, a mechanistic model of oleaginousness was unveiled, in which the indigenous and adopted NoDGAT2s formulated functional complementarity and specific transcript abundance ratio that underlie a rigid SFA:MUFA:PUFA hierarchy in triacylglycerol (TAG). By rationally modulating the ratio of NoDGAT2A:2C:2D transcripts, a bank of N. oceanica strains optimized for nutritional supplement or fuel production with a wide range of degree of unsaturation were created, in which proportion of SFAs, MUFAs, and PUFAs in TAG varied by 1.3-, 3.7-, and 11.2-fold, respectively. This established a novel strategy to simultaneously improve productivity and quality of oils from industrial microalgae.

Effect of Altering Dietary n-6:n-3 Polyunsaturated Fatty Acid Ratio with Plant and Marine-Based Supplement on Biomarkers of Bone Turnover in Healthy Adults.

Although there is accumulating evidence for a protective role of n-3 polyunsaturated fatty acids (n-3 PUFAs) on bone health, there are limited studies that examine the effect of altering dietary n-6:n-3 PUFA ratio with plant and marine sources of n-3 PUFA on bone health. Healthy adults (n = 24) were randomized into an eight-week crossover study with a four-week washout between treatments, with each subject consuming three of four diets. The four diets differed in the dietary n-6:n-3 PUFA ratios and either had an algal oil supplement added or not: (Control diet (10:1); α-linolenic acid (ALA) diet (2:1); Eicosapentaenoic acid/Docosahexaenoic acid (EPA/DHA) diet (10:1 plus supplement (S) containing EPA/DHA; Combination diet (2:1 + S)). The supplement was microalgae oil that provided 1 g EPA + DHA/day. Flaxseed oil and walnuts provided 8.6 g of ALA/day in the 2:1 diets. Serum levels of c-telopeptide (CTX), procollagen Type I N-terminal peptide, and osteocalcin showed significant correlation with age but none of the bone markers or peroxisomal proliferator-activated receptor-γ mRNA expression was significantly different between the diets. Serum CTX was negatively associated with red blood cell membrane linoleic acid and ALA and positively associated with membrane DHA. Neither altering dietary n-6:n-3 PUFA ratio from a 10:1 to a 2:1 ratio nor adding EPA/DHA supplement significantly changed bone turnover in the short term in healthy adults.

Markers of neuroprotection of combined EPA and DHA provided by fish oil are higher than those of EPA (Nannochloropsis) and DHA (Schizochytrium) from microalgae oils in Wistar rats

BackgroundTo overcome the current overexploitation of fish rich in n-3 long chain polyunsaturated fatty acids (LCPUFA), microalgae have become a promising marine lipid source. The purpose of this study was to assess eicosapentaenoic acid (EPA, 20:5n-3) and docosahexaenoic acid (DHA, 22:6n-3), isolated or combined from distinct marine origins, on the promotion of neuroprotective effects.MethodsThe experiment lasted for 10 weeks and involved 32 Wistar rats, divided into 4 diets (n = 8): a diet rich in milk fat was taken as control (Milk Fat) and compared to n-3 LCPUFA enriched diets, either in EPA + DHA form through fish oil (Fish Oil), or EPA through Nannochloropsis oil (Nanno), or DHA through Schizochytrium oil (Schyzo), while maintaining Milk Fat incorporation.ResultsPlasma lipid profile and dopamine levels were more beneficial in Fish Oil diet. In addition, n-3 LCPUFA incorporation was found increased in liver and erythrocytes from Fish Oil fed rats, suggesting that fish oil is a better dietary source for fatty acids deposition in the organism than microalgae. The Forced Swimming Test revealed a positive behavioural action of EPA + DHA, in opposition to Milk Fat and Nanno diets, which had higher immobile times. mRNA levels of serotonin receptors, HT1A and HT2A along with CREB, the transmission factor for learning and memory, were higher in the hippocampus of rats fed n-3 LCPUFA diets comparative to Milk Fat.ConclusionTaken together, the combination of EPA and DHA from fish oil can counteract the undesirable health effects of saturated fat based diets and benefit, in the long run, neurological function.

Simultaneous esterification and transesterification of microbial oil from Chlorella minutissima by acid catalysis route: A comparison between homogeneous and heterogeneous catalysts

Using low cost materials, tubular photo-bioreactors type bubble column were built for microalgae cultivation. Six factors/two levels Taguchi orthogonal array (L8) was adopted to identify the input variables with the greatest influence on oil accumulation by Chlorella minutissima. The function desirability was used to simultaneously analyze the process variables to attain maximum biomass concentration and lipid content. The microalgal oil was submitted to acid simultaneous esterification and transesterification reactions using homogeneous (H2SO4) and heterogeneous (Nb2O5/SO4) catalysts. Both catalysts afforded high biodiesel yield (>96%), although heterogeneous catalyst showed better yield (98%) and low residual glycerides at 4h reaction.

Valorization of Unconventional Lipids from Microalgae or Tall Oil via a Selective Dual Catalysis One-Pot Approach.

A dual catalysis approach enables selective functionalization of unconventional feedstocks composed of complex fatty acid mixtures with highly unsaturated portions like eicosapentaenoate (20:5) along with monounsaturated compounds. The degree of unsaturation is unified by selective heterogeneous hydrogenation on Pd/γ-Al2O3, complemented by effective activation to a homogeneous carbonylation catalyst [(dtbpx)PdH(L)]+ by addition of diprotonated diphosphine (dtbpxH2)(OTf)2. By this one-pot approach, neat 20:5 as a model substrate is hydrogenated to up to 80% to the monounsaturated analogue (20:1), this is functionalized to the desired C21 α,ω-diester building block with a linear selectivity of over 90%. This catalytic approach is demonstrated to be suitable for crude microalgae oil from Phaeodactylum tricornutum genetically engineered for this purpose, as well as tall oil, an abundant waste material. Both substrates were fully converted with an overall selectivity to the linear α,ω-diester of up to 75%.

Fatty acid profile and fuel-derived physico-chemical properties of biodiesel obtained from an indigenous green microalga, Desmodesmus sp. (I-AU1), as potential source of renewable lipid and high quality biodiesel

Organic sources of biodiesel such as microalgae are considered as potential renewable energy resources. These organisms are considered as sunlight-driven cellular factories that convert carbon dioxide to high amounts of lipids that can be used for biofuel production. This paper describes the possibility of using Desmodesmus sp. (I-AU1) for biodiesel production by evaluating its fatty acid profile distribution pattern and estimating the fuel-derived physical and chemical properties from fatty acid methyl esters (FAMEs) obtained from the trans-esterified microalgal oil. Growth rate, oil content, biomass, and lipid productivity of the algal strain have been investigated under nitrogen-starved (0.375 g L−1 NaNO3 in BG 11 medium) autotrophic condition for 22 days. Maximum average biomass yield of Desmodesmus sp. (I-AU1) is 0.745 g L−1 having 36.14% lipid content per dry weight of biomass, with a specific growth rate of 0.20 day−1. Fatty acid profiling of the biodiesel obtained from Desmodesmus sp. (I-AU1) contained total saturated fatty acid (SAFA) methyl esters of 31.02%, while the total monounsaturated fatty acid (MUFA) (C18:1) is 25.64%. Percentage composition of SAFA and MUFA for the microalga was 56.66%, which is high compared to that of most of related studies. Fuel properties were determined by empirical equations and were found to be within the limits of biodiesel standards ASTM D6751 (American) and EN 14214 (European). The quality properties of the biodiesel were low density (0.88 g cm−3), low kinematic viscosity (2.81 mm2 s−1), cetane number (43.47), oxidation stability (5.96 h), and cold filter plugging point (−7.41 °C). Hence, Desmodesmus sp. (I-AU1) has potential as a feedstock for the production of quality biodiesel.

Effect of docosahexenoic acid microalgae oil supplementation during pregnancy and lactation on levels of serum polyunsaturated fatty acid and tolerance to ovalbumin in suckling mice

Objective: To study the tolerance to ovalbumin (OVA) in suckling mice whose mothers had different doses of docosahexenoic acid (DHA) microalgae oil (DMO) supplementation during pregnancy and lactation. Method: According to different doses of DMO fed to mother mice during pregnancy and lactation, 66 suckling mice were divided into four groups. Suckling mice whose mothers were fed with 0.7% DMO were designated as low dose group (group L) (n=16), 2.1% DMO as middle dose group (group M) (n=16), 3.5% DMO as high dose group (group H) (n=17) and no DMO as control group (n=17). Before exposing to OVA, 8 suckling mice were killed in each group at 21-day-old. Remaining suckling mice were killed at 59-day-old after repeated OVA exposure. The serum polyunsaturated fatty acid (PUFA) levels of suckling mice were analyzed by high performance liquid chromatography (HPLC) at the age of 21- and 59-day.Histological examinations of jejunum were performed by HE staining and the mast cells in jejunum were observed by toluidine blue staining. OVA-IgE in serum, total IgA and OVA-IgA in the feces and IL-4 and IFN-γ in the supernatants of splenic mononuclear cells (SMC) were measured by ELISA. Real time PCR was performed to identify the gene expression of IL-10, TGF-β1 mRNA in SMC. Differences among groups were compared by one-way AVOVA and that between each group were compared by LSD. Result: In group M and H, the serum levels of n-3DHA (108±29)μg/ml; (102±34)μg/ml vs.(40±19)μg/ml (F=12.052, P=0.000)and n-3 eicosapentaenoic acid (6.7±2.3)μg/ml; (7.7±2.0)μg/ml vs. (3.9±1.1)μg/ml(F=9.573, P=0.000) were significantly higher than that in control group at the age of 21-day. The serum levels of n-3DHA were higher in group H (17.1±2.9)μg/ml than that in control group (5.9±3.3) μg/ml after repeated OVA exposure at the age of 59-day (F=10.339, P<0.000). Compared with control group (53±12) pg/ml, the levels of IL-4 in SMC in group H (42±9)pg/ml were lower (F=2.484, P<0.05). Conclusion: The serum levels of DHA in baby mice, whose mothers was fed with DMO during pregnancy and lactation, were significantly increased till adulthood. However, the effect on tolerance to OVA was limited.

Cultivation of microalgae for biodiesel production: A review on upstream and downstream processing

Fluctuating market price of fossil fuel and overwhelming emission of greenhouse gases to the atmosphere have resulted in climate change and have been a global concern in this decade. Hence, biodiesel has become an alternative option to fossil diesel as it is renewable and environmentally friendly. Nevertheless, this alternative fuel that is usually derived from terrestrial oil crops will cause shortage in food supply and deforestation if mass production is realized. In recent years, cultivation of aquatic microorganism (particularly microalgae) to produce biodiesel is considered as a practical solution due to their high growth rate and ability to synthesize large quantity of lipid within their cell. However, the development of energy and cost-efficiency of microalgae cultivation system are the main issues in producing renewable microalgae biodiesel. Of late, wastewater or organic compost has been used as the cultivation medium as it can provide sufficient nutrients to sustain microalgae growth. Microalgae cultivation method and system are vitally important as these factors undoubtedly affect the final microalgae biomass and lipid yield. In this review, the cultivation system of microalgae, nutrients demanded for microalgae production, cell harvesting and drying, microalgae oil extraction, and utilization of microalgae biomass for biodiesel production are introduced and discussed. It is anticipated to convey clearer perspectives in upstream and downstream processes in microalgae-derived biodiesel production.

Deoxygenation of Palmitic Acid on Unsupported Transition-Metal Phosphides

Highly active bulk transition-metal phosphides (WP, MoP, and Ni2P) were synthesized for the catalytic hydrodeoxygenation of palmitic acid, hexadecanol, hexadecanal, and microalgae oil. The specific activities positively correlated with the concentration of exposed metal sites, although the relative rates changed with temperature due to activation energies varying from 57 kJ mol–1 for MoP to 142 kJ mol–1 for WP. The reduction of the fatty acid to the aldehyde occurs through a Langmuir–Hinshelwood mechanism, where the rate-determining step is the addition of the second H to the hydrocarbon. On WP, the conversion of palmitic acid proceeds via R-CH2COOH → R-CH2CHO → R-CH2CH2OH → R-CHCH2 → R-CH2CH3 (hydrodeoxygenation). Decarbonylation of the intermediate aldehyde (R-CH2COOH → R-CH2CHO → R-CH3) was an important pathway on MoP and Ni2P. Conversion via dehydration to a ketene, followed by its decarbonylation, occurred only on Ni2P. The rates of alcohol dehydration (R-CH2CH2OH → R-CHCH2) correlate with the concen...

Recent progress in catalytic conversion of microalgae oil to green hydrocarbon: A review

Abstract The increase in greenhouse gas emission due to the burning of fossil fuels since the last century has led to global warming. This has triggered numerous researches in green hydrocarbon alternatives from renewable oil. Microalgae is one of the potential sources of green hydrocarbon, which will reduce the dependency on fossil fuel. This is because microalgae have a high oil or lipid content, rapid growth rate, and high ability to sequester carbon dioxide. Besides that, their cultivation does not require arable land and will, therefore not compete with global food production. The current biofuel production is based on the transesterification of triglyceride to biodiesel which suffered from several drawbacks such as high acidity, high viscosity, and low heating value, etc . A more efficient reaction route needs to be developed to produce biofuel which possesses similar properties as the fossil-derived fuel. Therefore, this review aims to encompass the conversion of microalgae oil towards green hydrocarbons via various catalytic reactions. The fundamental chemistry and mechanisms involved in the conversion of microalgae oil to useful chemical products are also discussed in detail.

Effects of dietary docosahexaenoic acid sources, microalgae meal and oil, on growth, fatty acid composition and docosahexaenoic acid retention of orange-spotted grouper,Epinephelus coioides

This study evaluated the effects of Aurantiochytrium spp. microalgae meal and oil as dietary docosahexaenoic acid (DHA) sources on the growth, fatty acid composition and DHA retention of orange-spotted grouper, Epinephelus coioides. Dietary fish oil was replaced with microalgae meal or oil to provide an equal amount of DHA as a fish oil-containing basal diet. In total, three experimental diets were fed to triplicate groups of fish (initial wt: 8.48 ± 0.06 g) in a recirculating system for 8 weeks. The weight gain and feed efficiency of the fish did not differ significantly among the experimental diets. The fatty acid composition of the whole body of the fish generally reflected the composition of their diet. The concentration of eicosapentaenoic acid in the whole body was higher in the fish fed the fish meal control diet than in those fed the two experimental diets The fish fed the control diet and those fed the diet containing microalgae oil exhibited higher DHA concentrations than did the fish fed the diet containing microalgae meal. The whole-body DHA retention was the highest in the fish fed the diet with microalgae oil, followed by the fish fed the control diet. The lowest whole-body DHA retention was observed in the fish fed the diet containing microalgae meal. The results suggested that the oil from Aurantiochytrium spp. microalgae can be used as DHA source for the grouper. DHA utilization by the fish was higher when the diet was supplemented with microalgae oil than with dry microalgae meal.

Isolation and Selection of Microalgal Strains from Natural Water Sources in Viet Nam with Potential for Edible Oil Production.

Industrial vegetable oil production in Viet Nam depends on oil seeds and crude plant oils that are currently more than 90% imported. As the first step in investigating the feasibility of using microalgae to provide Viet Nam with a domestic source of oil for food and edible oil industries, fifty lipid-producing microalgae were isolated and characterized. The microalgae were isolated from water sources ranging from freshwater to brackish and marine waters from a wide geographic distribution in Viet Nam. Initial analyses showed that 20 of the 50 strains had good growth rates, produced high biomass and had high lipid content, ranging up to 50% of dry weight biomass. 18S rRNA gene sequence analyses of the 50 strains showed a great diversity in this assemblage of microalgae, comprising at least 38 species and representatives of 25 genera: Chlamydomonas, Poterioochromonas, Scenedesmus, Desmodesmus, Chlorella, Bracteacoccus, Monoraphidium, Selenastrum, Acutodesmus, Mychonastes, Ankistrodesmus, Kirchneriella, Raphidocelis, Dictyosphaerium, Coelastrella, Schizochlamydella, Oocystidium, Nannochloris, Auxenochlorella, Chlorosarcinopsis, Stichococcus, Picochlorum, Prasinoderma, Chlorococcum, and Marvania. Some of the species are closely related to well-known lipid producers such as Chlorella sorokiniana, but some other strains are not closely related to the strains found in public sequence databases and likely represent new species. Analysis of oil quality showed that fatty acid profiles of the microalgal strains were very diverse and strain-dependent. Fatty acids in the microalgal oils comprised saturated fatty acids (SFAs), poly-unsaturated fatty acids (PUFAs), and mono-unsaturated fatty acids (MUFAs). The main SFA was palmitic acid. MUFAs and PUFAs were dominated by oleic acid, and linoleic and linolenic acids, respectively. Some strains were especially rich in the essential fatty acid α-linolenic acid (ALA), which comprised more than 20% of the fatty acids in these strains. Other strains had fatty acid compositions similar to that of palm oil. Several strains have been selected on the basis of their suitable fatty acid profiles and high lipid content for further chemical and physical characterization, toxicity and organoleptic tests of their oils, and for scale-up.

ALGAE OIL EXTRACTION FROM FRESHWATER MICROALGAE Chlorella vulgaris

This research aims to investigate the optimum condition of oil extraction method to extract maximum oil yield from freshwater microalgae Chlorella vulgaris. The modified soxhlet extraction method was used to identify the best solvent systems which are heptane, heptane: methanol (1:1), heptane: methanol (1:2), heptane: ethanol (1:1) and heptane: ethanol (1:2) for extracting the microalgae oil. The effect of different mixing rate (rpm), temperature (oC) and extraction time (hours) were carried out using the optimized solvent system to evaluate the optimum condition of oil extraction. Based on the yield of oil extraction, heptane alone become the best solvent to extract the oil with the yield of 57.5%, followed by heptane: methanol (1:2), heptane: ethanol (1:1), heptane: ethanol (1:2) and heptane: methanol (1:1) with the yield of 47.5%, 44.8%, 43.2% and 41.4%, respectively. Maximum oil quantity of 61.27% was obtained after extracted the Chlorella vulgaris biomass using heptane as a solvent at the following optimal conditions: mixing rate of 600 rpm, temperature of 65 °C and extraction time of 5 hours. This study confirmed that an increasing temperature resulted in the increased of oil yield, but at higher temperature (greater than 65 °C), the oil yield was decreasing. Too high of temperature in oil extraction may cause partial decomposition of the microalgae cells and thus lowering the yield of oil extracted.

Microalgal Oil from Schizochytrium sp. Prevents HFD-Induced Abdominal Fat Accumulation in Mice

ABSTRACTObjective: Dietary n-3 polyunsaturated fatty acids (PUFAs), especially eicosapentaenoic acids (EPA) and docosahexaenoic acid (DHA), are proved to be effective in obesity reduction. Microalgal oil (MO) is an important alternative source of n-3 PUFAs that effectively alleviates obesity. The aim of the present study was to explore the anti-obesity effects of microalgal oil from Schizochytrium sp. (SMO) and to compare the effects of 2 SMOs (SMO1 and SMO2) with different levels of purity of n-3 PUFAs on high fat diet (HFD)-induced obesity in male C57BL/6J mice.Methods: Mice were randomly divided into 5 groups: (1) regular chow (RC); (2) HFD; (3) HFD + fish oil (FO); (4) HFD + SMO1; and (5) HFD + SMO2. Body weight and food intake were weekly monitored. After 16 weeks of treatment, a glucose tolerance test (GTT) and an insulin tolerance test (ITT) were performed. Serum lipid profile, morphological changes in the liver and epididymal white adipose tissue (eWAT), and the mRNA expression of lipid metabolism–related genes were also examined.Results: SMO treatment significantly decreased HFD-induced abdominal fat accumulation, lowered the levels of triglycerides, cholesterol, and low-density lipoprotein, as did the positive control treated with FO. Morphological examination revealed a remarkable reduction in lipid droplet formation in the liver tissue and the particle size of eWAT. An alleviation of inflammation infiltration in eWAT caused by a high-fat diet was also observed. Real-time reverse transcription–polymerase chain reaction analysis examination confirmed that microalgal oil inhibited the gene expression of fatty acid synthase, sterol responsive element-binding protein-1c, and acetyl-CoA carboxylase but promoted that of hormone-sensitive lipase and lipoprotein lipase, carnitine palmitoyltransferase-1, and uncoupling proteins in the liver and eWAT. Moreover, similar anti-obesity effects were obtained with the same dosage but different purity of n-3 PUFAs.Conclusions: As an alternative n-3 PUFAs resource, dietary intake of SMO might be beneficial to prevent HFD-induced abdominal fat accumulation.

Extraction of hydrocarbons from freshwater green microalgae (Botryococcus sp.) biomass after phycoremediation of domestic wastewater

ABSTRACTThis study was undertaken to analyze the efficiency of Botryococcus sp. in the phycoremediation of domestic wastewater and to determine the variety of hydrocarbons derived from microalgal oil after phycoremediation. The study showed a significant (p < 0.05) reduction of pollutant loads of up to 93.9% chemical oxygen demand, 69.1% biochemical oxygen demand, 59.9% total nitrogen, 54.5% total organic carbon, and 36.8% phosphate. The average dry weight biomass produce was 0.1 g/L of wastewater. In addition, the dry weight biomass of Botryococcus sp. was found to contain 72.5% of crude oil. The composition analysis using Gas Chromatogram - Mass Spectrometry (GC-MS) found that phthalic acid, 2-ethylhexyltridecyl ester (C29H48O4), contributed the highest percentage (71.6%) of the total hydrocarbon compounds to the extracted algae oil. The result of the study suggests that Botryococcus sp. can be used for effective phycoremediation, as well as to provide a sustainable hydrocarbon source as a value-added chemical for the bio-based plastic industry.

Ni/Co-Natural Clay as Green Catalysts for Microalgae Oil to Diesel-Grade Hydrocarbons Conversion

The Ni/Co-natural clay catalysts have been prepared for the conversion of algae oil into diesel-grade hydrocarbons. Methyl oleate was used as a model compound for the present study. Ni/clay catalyst promotes decarboxylation/decarbonylation, whereas remarkable selectivity in hydrodeoxygenation (HDO) is achieved with Co/clay catalysts. Powder XRD and DRS studies of substrate mixed catalysts reveal a more prominent adsorption of substrate molecules over the Ni surface, which results in low HDO selectivity of nickel catalysts by surpassing the essential contribution of acidic sites. The HDO process provides higher carbon atom economy and energy value over decarboxylation/decarbonylation, while further reducing the formation of greenhouse gases such as CO2 and CH4. Total yield of saturated hydrocarbons from algae oil was 84–86 wt % with similar selectivity. The HDO rates of different fatty acids present in algae oil were independent of the fatty acid chain length. The catalysts are cost-effective and recyclabl...

Comparative life cycle assessment study on environmental impact of oil production from micro-algae and terrestrial oilseed crops

In this study the LCA methodology is applied in order to satisfy two goals: i) to evaluate the hot spots in site-specific production chain of biodiesel from terrestrial and micro-algae feedstock; ii) to compare quantitatively, utilizing primary data, the impacts of the first generation in respect to the third generation bio-fuels. Results show that micro-algae are neither competitive yet with traditional oil crops nor with fossil fuel. The use of renewable technologies as photovoltaics and biogas self production might increase the competitiveness of micro-algae oil. Further investigations are however necessary to optimize their production chain and to increase the added value of co-products.

Optimization of extraction of lipid from Isochrysis galbana microalgae species for biodiesel synthesis

ABSTRACTMicroalgae are promising alternative plant sources for biodiesel production because of the significant increase in lipid yield through heterotrophic cultivation and genetic engineering approaches. This study aims to evaluate the extraction and conversion of lipids from Isochrysis galbana. Response surface methodology (RSM) was used to optimize lipid extraction and thereby obtain high yields from the four microalgae species. The optimal lipid yields for Isochrysis galbana is 8.41 wt%. Moreover, the dominant lipid composition found from Isochrysis galbana extractions was palmitic acid (C16:0) at 22.3%. The high saturated acid of Isochrysis galbana contributed to the improved biodiesel properties because biodiesel quality is influenced by the lipid composition of microalgae species. The study employed the two-step esterification–transesterification process to convert the microalgae oil into biodiesel, glycerol, and water. The FAME content is 99.7% under the methanol to oil molar mass of 12:1, 1 wt%, 65°C, and 800 rpm. Furthermore, the main biodiesel properties, such as viscosity, higher heating value, and iodine value, were measured according to ASTM D6751 and EN 14124. Results show that microalgae oil can potentially be used as biofuel in future applications.

Obtaining biodiesel from microalgae oil using ultrasound-assisted in-situ alkaline transesterification

Efficiency of in-situ alkaline transesterification of dry biomass from a crop of Spirulina sp., using ultrasound-assisted and/or the addition of different co-solvents to the reaction medium was studied.The starting biomass had a total lipid content of 7.0% (Folch method), comprised mainly by the following fatty acids: 16:0 (44.2%), 18:3 (n–6) (23.3%), and 18: 2 (n–6) (11.1%).When the transesterification reaction was carried out without ultrasound, it only extracted 12.8% of lipids (0.9% of the biomass) after 2h of reaction, achieving only a 63.6% ester content. When the process was carried out under the same conditions except for the ultrasound-assisted (80W), the weight yield remained mostly unchanged, but the ester content increased to 97.6%. Additionally, when chloroform was added to methanol as a co-solvent in a 2:1 ratio it was possible to extract 43% of lipids. However, the ester content was reduced to 69.7%. Moreover, with maximum ultrasound power (180W) a high ester content (96.9%) and a relatively high extraction yield (26%) were obtained, even without the co-solvent.These results show that the ultrasound significant increased the yield of the in-situ alkaline transesterification of Spirulina sp. biomass, promoting a higher percent recovery of lipids as well as ester content from the starting material.

Heterogeneous-catalysed direct transformation of microalga biomass into Biodiesel-Grade FAMEs

The production of biodiesel using microbial lipids is attractive as oleaginous microorganisms can accumulate significant amounts of lipids (>20%) and they do not compete with food production. However, the poor economic viability of the production process involving cell harvest, microalga oil extraction, lipid transesterification and esterification reactions as well as biodiesel purification leads to a non-viable biodiesel production process. Thus, lipid transesterification and esterification optimization in addition to biodiesel purification, are important limiting factors for this process. The present research is focused on the optimization of the reaction conditions in order to obtain a high conversion to FAMEs in the direct biodiesel production from the microalgae N. gaditana using the CT-269 ion-exchange resin. The process was analysed by following the factorial design and response surface methodology concluding that optimum values of the variables are a temperature of 95°C, a mass ratio of catalyst to microalga of 0.52/1, and a mass ratio of methanol to microalga of 33/1. Besides, the properties of the crude biodiesel were evaluated according to EN 14214 and ASTM D6751 standards, indicating that it is necessary an additional downstream purification step to remove all components that defile the final biodiesel. After an a two-step purification method that combined wet and dry treatments, ASTM D6751 biodiesel grade-FAMEs were obtained for the properties evaluated. The biodiesel also met all the properties determined according to EN 14214 except for the content of polyunsaturated FAMEs, the iodine value, oxidation stability and the cetane number.