Microalgae Oil Research Articles

Microalgae Oil-Based Metal Working Fluids for Sustainable Minimum Quantity Lubrication (MQL) Operations—A Perspective

This article presents a perspective on the potential use of microalgae oils in the production of metal working fluids (MWFs) used for minimum quantity lubrication (MQL) operations. The generalities of MQL operations and requirements of MWFs, and current advances in the development of the most promising microalgae oils with high contents of saturated, monounsaturated, and polyunsaturated fatty acids were reviewed and discussed. The analysis of data, discussions, and conclusions of numerous studies published recently and combined with the experience of the multidisciplinary team of authors strongly suggest that microalgae oils do indeed have great potential as sustainable and eco-friendly base oils for producing semi-synthetic MWFs, soluble oils and straight cutting fluids for MQL operations. Additionally, gaps and challenges focused on the use of agro-industry wastewater in microalgae production, green harvesting and oil extraction methods, and replacement of toxic additives in MWFs by green nanoparticles and biopolymers were identified and highlighted for achieving massive microalgae oil-based MWFs production and truly green machining processes.

Kinetic and thermodynamic evaluations of oil extraction from immobilized Chlorella vulgaris using different solvents

Investigating the effect of different solvents used for microalgae oil extraction on the determinations of kinetic values and thermodynamic parameters is a compelling novel approach for the current study. The primary concern of microalgae oil extraction is selecting a solvent system because it has a massive influence on the extraction yield, composition, and oil quality. Three different solvent systems were inspected to determine the suitable solvent for the oil extraction from immobilized Chlorella vulgaris: heptane, heptane:methanol, and heptane:ethanol. The research methodology begins with the immobilization of microalgae cells. The matured immobilized beads were then harvested, and dried biomass was recovered. The oil was extracted by solvent extraction method using the solvents mentioned. Finally, the extracted oil was trans-esterified and analyzed for fatty acid methyl ester profile. Based on the results calculated, heptane is determined to extract the most oil with 27.42 %, followed by H:M and H:E at the highest temperature and longest running time. When the polar solvent is mixed with a non-polar solvent, the mixture has the least kinetic value and immense activation energy. However, the activation energy for heptane is only 89.06 kJ/mol. Another essential objective of this research is to determine the effects of solvents on the thermodynamics parameters. The extraction process of microalgae oil using heptane alone is determined to have a ΔH value of 0.111 kJ/mol, followed by 0.201 and 0.102 kJ/mol for solvent system H:M and H:E respectively. All the values obtained are positive, thus making the extraction processes using various solvents to be endothermic. The positive values of ΔS and the negative values of ΔG indicated that the oil extraction using heptane is thermodynamically spontaneous and irreversible, thus making it economically feasible. The fatty acids methyl esters such as palmitic, stearic, oleic, linoleic, and linolenic were the prime constituents quantified in the oil extracted using heptane compared to other solvent systems. Therefore, with the larger and increasing kinetic values and lowest activation energy, it can be concluded that heptane is the most suitable solvent for the oil extraction of immobilized Chlorella vulgaris compared to other solvent systems employed in the current research work.

Algal oil gives control of long‐chain omega‐3 levels in full‐cycle production of Atlantic salmon, without detriment to zootechnical performance and sensory characteristics

AbstractThe levels of eicosapentaenoic (EPA) and docosahexaenoic (DHA) in salmon fillets have decreased because of the progressive replacement of fish oil (FO). This study contributes to enabling the sustainable growth of aquaculture by confirming the effects of partially or fully replacing FO with microalgal oil (AO) on growth, muscle fatty acid profiles, and muscle quality of farmed Atlantic salmon. Crucially, this is now done throughout the entire post‐smolt production cycle and up to a harvest weight of 3 kg. Three experiments were performed using fish ranging from 145 g to 3 kg and testing different diets, replacing FO up to 100%. Zootechnical performance was similar among treatments in all experiments. Changing the lipid source in the diet resulted in EPA and DHA digestibility of greater than 96%. Sensory characteristics of raw fish fillets were similar among treatments, supporting a similar sensorial experience with the replacement of FO with no impact on consumers. Overall, results confirm that the AO tested here enables the sustainable growth of Atlantic salmon aquaculture by helping to maintain a level of EPA and DHA in the fish fillets, without detriment to zootechnical performance and sensory characteristics, while simultaneously contributing to a reduced marine footprint for aquafeeds.

Nutritional innovations in superior European sea bass (Dicentrarchus labrax) genotypes: Implications on fish performance and feed utilization

The sustainable development of the aquaculture industry relies on the use of alternative conventional and emergent raw materials that contributes to a circular economy and to reduce the dependency on fish meals and fish oils coming from oceanic fish populations. Additionally, the genetic selection of farmed fish that can display higher growth and feed utilization when fed alternative feeds, is pointed out to be a complementary valuable tool to facilitate the implementation of circular economy approaches. The main purpose of the present study was to determine the effectiveness of genetic selection for growth in European sea bass, in response to a challenge with an alternative diet that aimed to partially replaced fishmeal (FM) by poultry meal (PM) and totally replace fish oil (FO) by a blend of poultry oil (PO) with a novel microalgae oil. The two families of fish juveniles were obtained by in vitro fertilization of selected for a multi-trait including high growth (genetically selected, GS) or non-selected (wild type, WT) broodstocks and then were nutritionally challenged with a control diet that mirrored a standard commercial diet with fishmeal (20%) and fish oil (7%), or a Future diet that partially replaced the FM by PM and totally replaced the FO by a blend of rapeseed oil, PO, and a novel DHA rich-algal oil. From the second month of feeding until the end of the trial, European sea bass that was selected since for 7 generations performed better in terms of growth than the wild-type genotype, possibly related with an apparent favored feed and nutrient utilization. Furthermore, selection decreased the perivisceral fat and increased the nutritional value of flesh by increasing DHA (in g/ 100 g flesh) and ARA contents. In contrast, the dietary treatment showed little effect on fish growth performance, denoting the successful partial replacement of FM by PM and the total replacement of FO by a blend of poultry oil and an emergent microalgal oil. However, Future diet tended to reduce the ADCs of some amino acids, as well as showed an additive effect to genotype in increasing the n-3 PUFA of flesh. Altogether, our data demonstrate that multi-trait genetic selection of European sea bass improve fish plasticity to cope with the variations of ingredients in alternative feeds with low FM/FO.

Supranutrition of microalgal docosahexaenoic acid and calcidiol improved growth performance, tissue lipid profiles, and tibia characteristics of broiler chickens

BackgroundDocosahexaenoic acid (DHA) and calcidiol could be enriched in chicken for improving public nutrition and health. It remains unclear if supranutritional levels of DHA and calcidiol impair growth performance or metabolism of broiler chickens. This study was to determine singular and combined effects of high levels of supplemental DHA-rich microalgal biomass or oil and calcidiol on growth performance, concentrations of triglycerides, cholesterol, and nonesterfied fatty acids in plasma, liver, breast, and thigh, and biophysical properties of tibia.MethodsIn Exp. 1, 144 day-old Cornish chicks were divided into 4 groups (6 cages/treatment, 6 birds/cage), and were fed a corn-soybean meal basal diet (BD), BD + 10,000 IU calcidiol/kg (BD + Cal), BD + 1% DHA-rich Aurantiochytrium (1.2 g DHA/kg; BD + DHA), and BD + Cal + DHA for 6 weeks. In Exp. 2, 180 day-old chicks were divided into 5 groups, and were fed: BD, BD + DHA (0.33% to 0.66% oil, 1.5 to 3.0 g DHA/kg), BD + DHA + EPA (1.9% to 3.8% eicosapentaenoic acid-rich Nannochloropsis sp. CO18, 0.3 to 0.6 g EPA/kg), BD + DHA + calcidiol (6000 to 12,000 IU/kg diet), and BD + DHA + EPA + Cal for 6 weeks.ResultsBirds fed BD + Cal diet in Exp. 1 and BD + DHA + EPA diet in Exp. 2 had higher (P < 0.05) body weight gain (10%–11%) and gain:feed ratio (7%), and lower (P < 0.05) total cholesterol and triglyceride concentrations in plasma (18%–54%), liver (8%–26%), breast (19%–26%), and thigh (10%–19%), respectively, over the controls. The two diets also improved (P < 0.05) tibial breaking strength (8%–24%), total bone volume (2%–13%), and (or) bone mineral density (3%–19%) of chickens.ConclusionSupranutrition of dietary calcidiol and DHA alone or together did not produce adverse effects, but led to moderate improvements of growth performance, lipid profiles of plasma and muscle, and bone properties of broiler chickens.

Optimization of cavitation-assisted biodiesel production and fuel properties from Neochloris oleoabundans microalgae oil using genetic algorithm and response surface methodology

Biodiesel is a promising alternative fuel for diesel engines that provides energy security and significant environmental benefits. But its commercialization is restricted due to the cost and quality as compared to diesel fuel. To address the above, Neochloris oleoabundans microalgae oil, a non-edible, cost-effective, and underutilized third-generation feedstock, is used to produce superior biodiesel by the transesterification reaction using a hydrodynamic cavitation (HC) approach. In this research work, the transesterification model for microalgae biodiesel production is optimized through genetic algorithm (GA) and response surface methodology (RSM) using MATLAB R2020a and Design Expert 8.0.7.1, respectively. Four process input variables (operating pressure (0.5–2.5 bar), catalyst concentration (0.5–1.5 wt.%), reaction time (5–25 minutes), and molar ratio (3:1 to 7:1)) and a five-level L30 array were developed to construct a statistical model. Biodiesel yield and major properties like density, kinematic viscosity, calorific value, and flash point are the model responses. The optimum conditions for microalgae biodiesel production were operating pressure of 2.43 bar, KOH catalyst concentrations of 1.22 wt. %, reaction time of 15.54 minutes, molar ratio of 5.61:1 and at 60°C fixed reaction temperature. The optimum value of response, such as biodiesel yield, was 99.80%, the density was 0.882 g/cc, the kinematic viscosity was 4.06 cst, the calorific value was 41.72 MJ/kg, and the flash point was 146.64 °C. RSM and GA predicted results were validated experimentally. The reaction time for biodiesel produced by HC in the same settings as the conventional method was reduced by 85%. Due to its faster processing time, the HC approach is preferred to the conventional method.

Performance of bleaching clays in dechlorophyllisation of microalgal oil: A comparative study

While clay has been extensively studied for its ability to remove chlorophyll from vegetable oil, its effects and suitability on microalgae oil have received far less attention. In this study, three different clay types are evaluated and compared for their ability to dechlorophyllise microalgae oil. The clays involved are kaolinite, Fuller’s earth and bentonite clay which are activated by acid treatment. Bentonite clay is found to remove chlorophyll effectively (76.04%) than kaolinite and Fuller’s earth due to the presence of porous materials that facilitate adsorption. Additionally, the conditions of high temperature (79.69%) and ultrasound treatment (84.24%) demonstrate satisfactory chlorophyll removal efficiency. Another promising finding is that chlorophyll can be adsorbed on the clays without affecting the lipid composition in the microalgae extract significantly. Spent bleaching clay disposal is a growing issue that poses an environmental burden. Reusing bleaching clay can lower expenses and increase oil recovery. In a single sequential run, using spent bentonite clay yields the outcomes comparable to those of virgin bentonite clay. This finding offers a useful green and environmentally friendly approach to remove chlorophyll from microalgae oil feedstock.

Microalgae oil firm Checkerspot raises cash

Checkerspot, one of C&EN’s 10 Start-Ups to Watch in 2018, has raised $55 million in a series C financing round led by ArrowMark Partners and supported by Cox Enterprises. The company, which is headquartered in California, derives polyols from microalgae- based oils. These polyols are made into polyurethanes used in its WNDR Alpine line of skis and snowboards.

Encapsulated paracetamol-based eutectic solvents for the treatment of low-grade palm oil mixed with microalgae oil

The development of an efficient and green catalyst is a key step for the esterification of free fatty acid (FFA) in non-edible oil feedstocks. This study introduces a novel acidic deep eutectic solvent (DES) catalyst derived from an active pharmaceutical ingredient for FFA esterification. The DES was formed by paracetamol and p-toluenesulfonic acid monohydrate (PTSA), as the hydrogen bond acceptor (HBA) and the hydrogen bond donor (HBD) components, respectively. The DES was encapsulated in medical capsules for the loading and handling steps; and they utilized to esterify a high content of FFA (8.11%) in a low-grade palm oil-microalgae oil mixture to achieve an acceptable FFA limits (<2%) for transesterification reaction. The FFA content was decreased to < 2% under optimum conditions (catalyst dosage 2% wt/wt of catalyst to oil, 10:1 molar ratio of methanol to oil at 60 °C for 60 min reaction time). Paracetamol forms a eutectic mixture with PTSA and is an effective HBA component in the formation of the DES catalyst. The analysis of relative solubility screening, σ-profile and σ-potential confirm certain level of solubility and homogeneity of this DES in methanol during the pre-treatment process. The formation of the eutectic mixture endows the catalyst with advantages for the esterification reaction such as improvements in recyclability and hygroscopicity of PTSA.

Investigation on the emulsification mechanism in aqueous enzymatic extraction of edible oil from Schizochytrium sp.

The interaction between emulsified substances and lipids generates an emulsification system during the extraction of microalgae edible oil by aqueous enzymatic method. This study aimed to resolve the dynamics of interfacial protein adsorption during the extraction of microalgae oil at different enzymatic times and the effect on the stability of the interfacial membrane formed by the proteins based on interfacial effects. At 1.5h of enzymatic hydrolysis, the molecular weights of the proteins/peptides were all below 35 kD. In addition, the protein-peptide structure was loose, with the lowest number of disulfide bonds, peak surface hydrophobicity, the highest number of residues, and disordered lipid acyl arrangement. At the same time, the physical stability of the emulsion was the lowest, and the interfacial membrane rupture was distinct. On excessive enzymatic hydrolysis (at 3.0h), a more uniform interfacial membrane was re-formed on the lipid surface. Protein is the main emulsifying substance in the emulsification system. The addition of protease affects the stability of the interfacial membrane formed by proteins. In addition, sufficient enzymatic hydrolysis (1.5h) inhibited emulsification, while excessive enzymatic hydrolysis (3.0h) promoted emulsification. © 2023 Society of Chemical Industry.

EDITORIAL

The editorial of Thermal Engineering of this issue continues the discussion on scientific research needs in vital areas in which thermal engineering has important participation. The main goal is to motivate the readers, within their specialties, to identify possible subjects for their future research. The ever growing global energy demand requires de development of alternative fuels. That demand has propelled the search for viable sources of clean energy. The investment in research and development in renewable energy has increased in recent years and the economic viability of those sources of energy has become closer to reality. One of the major downsides of the production of biofuels from vegetal sources is the use of land that would be used to produce food to produce agricultural products that will be used to produce fuel. Taking that context in consideration, the development of a methodology economically viable that produces biofuels and bioproducts from microalgae is a solution that meets the criteria aforementioned. Energy applications is the biggest assets of microalgae growth; it can generate biohydrogen, biodiesel and biogas. Biodiesel is produced from microalgae oil, gas methane is produced by the anaerobic digestion (AD) of microalgae biomass and biohydrogen is produced by photolysis in the photochemical step of the photosynthesis. Hydrocarbons with similar composition of jet fuel can be obtained from microalgae by distillation. Other than that, microalgae can be used as supplies for pharmaceutical companies with high added value product as carotenoids, for example. Microalgae can be produced in photobioreactos (PBR’s). PBR’s are designed in a way that do not compete with the use of land for produce. The mission of Thermal Engineering is to document the scientific progress in areas related to thermal engineering (e.g., energy, oil and renewable fuels). We are confident that we will continue to receive articles’ submissions that contribute to the progress of science.

Performance analysis of a CI engine powered by different generations of biodiesel; Palm oil, Jatropha, and microalgae

Biodiesels from various biodegradable feedstocks are being researched to replace conventional fuels. This study aims to analyse and compare the combustion behaviour of a CI engine with different generations of biodiesel by evaluating its performance in terms of heat release, temperature, pressure, fuel consumption, thermal efficiency, and ignition delay. The research was performed on a direct injection, one-cylinder, liquid-cooled CI engine using diesel and a 20 % blend level of biodiesel made from three different generations of biodiesel, i.e., palm oil, Jatropha oil, and microalgae oil. The performance of the diesel engine was evaluated with a variable load of 25 to 100 %, and a comparison was made between the various fuels. The findings show that the value lies between 31.52 and 34.80 J/deg. for heat release rate, 70.11–73.11 bars for cylinder pressure, 12.71–13.94 deg. for ignition delay, 551.97–568.13 K for exhaust gas temperature, 31.86–32.67 % for brake thermal efficiency, 259.31–289.35 g/kWh for brake-specific fuel consumption, and 425.5–876.65 ppm for NOx emissions, at 100 % load. The M20 outperforms all other biodiesels. The results justified the use of biodiesel in contemporary diesel engines and made it a significant contributor to replacing fossil fuels.

Advanced treatment of secondary effluent from wastewater treatment plant by a newly isolated microalga Desmodesmus sp. SNN1.

Secondary effluents contain considerable amounts of nitrogen and phosphorous, which if dumped untreated can cause eutrophication of the receiving water bodies. Microalgae can remove these nutrients and other pollutants from the wastewater effluents and play an effective role in the secondary effluent treatment. In this study, six microalgae strains (SNN1, SNN2, SNN3, SNN4, SNS1, and SNS2) were isolated and screened from the water and mud of Yingxue Lake of Shandong Jianzhu University, and their efficiencies for the removal of COD, NH4 +-N, TN, and TP in the secondary effluent were assessed. By comparing the growth performances and nutrient removal ability of algal strains in domestic sewage, we found that SNN1 (identified and named as Desmodesmus sp. SNN1) has the highest efficiency for biomass accumulation and sewage purification. Hence, the algal strain SNN1 was selected for further screening and optimization experiments. The strain showed higher biomass yield and better nutrient removal rate when the pH of secondary effluent was 9.0 and the initial inoculum concentration (optical density at 680 nm) of algal strain was 0.4. After 12 days of treatment, the concentrations of COD, NH4 +-N, TN, and TP in the secondary effluent were 31.79, 0.008, 8.631, and 0.069 mg/L, respectively. Therefore, SNN1 with the removal rates of 52.69% (COD), 99.99% (NH4 +-N), 89.09% (TN), and 94.64% (TP) displayed its high potential in nutrient removal. In addition, it also yielded 5.30 mg/L of chlorophyll a and 168.33 mg/L of lipids. These results demonstrated that this strain exhibited an effective treatment capacity for secondary effluent and microalgal oil production. This study is helpful to provide a strategy for the resource utilization of secondary effluent and the conservation of freshwater resources required by microalgae culture.

Advances in Biodiesel Production from Microalgae

Biofuels, as a renewable, eco-friendly, and cost-effective energy source, can reduce the dependence on fossil fuels. The researchers considered different approaches for obtaining high biodiesel yields from microalgae biomass. This work aims to present an overview of the feasibility of microalgae use in biodiesel production. Therefore, biodiesel production from microalgae oil via the transesterification process was explained in detail. The application of non-catalytic transesterification and catalytic transesterification was reviewed. The achievements in the application of homogenous catalysts, heterogeneous catalysts, and enzymatic catalysts for microalgae oil transesterification were discussed. The present technologies for biodiesel production from microalgae need more improvements to increase their efficiencies and reduce costs. Therefore, future research should focus on the development of effective catalysts for biodiesel production from microalgae biomass.

Synthesis and properties of coal dust suppressant based on microalgae oil extraction

Dust suppression is an important method for improving the effect of wet dust removal in coal mines. With the aim of overcoming the challenges of weak interfacial performance and the poor dust suppression effect caused by traditional coal dust suppressants under hard water conditions, a new method for extracting microalgae oil to synthesize coal dust suppressants is proposed here. The optimized conditions of microalgae oil extraction were analyzed by single-factor experiments and a response surface methodology. A microalgae oil-based coal dust suppressant (MODS) was synthesized from the extracted microalgae oil and its structure was determined. Property and performance tests were carried out under hard water conditions and the influence of hardness conditions on the dust reduction effect of the MODS was analyzed. The results show that a solvent ratio of 2.04:1, a liquor-to-material ratio of 4:1 and an extraction time of 4 h were the optimal extraction conditions for the microalgae oil. The MODS is an amide dust suppressant with an average tolerance of calcium concentration of 1271.28 mg·L−1, which had good resistance to hard water. Under the hard water conditions, the surface tension of the MODS remained at 31.8–33 mN·m−1 when the temperature, pH and salinity changed greatly (temperature of ≤60 °C, pH of 2–13 and NaCl mass fraction of ≤43 %). The dynamic contact angles of sodium dodecyl benzene sulphonate (SDBS) and the MODS at 60 s were 26.78° and 13.41°, respectively, and the sinking time of coal dust in the MODS solution was significantly smaller than that in the SDBS solution at the same concentration. This implied that the MODS performed better with regards to wettability than the commonly used anionic surfactant SDBS. This study lays an important foundation for the development of green and hardwater-resistant coal dust suppressants.

Microalgae lipid extraction: a novel lab-scale method within a biorefinery approach (fractioning)

Extraction and fractioning of microalgal lipids have been recurrently studied because of the market value of certain lipid families (i.e. carotenoids and xanthophylls) and the opportunity that microalgal oils represent for obtaining biofuels. Most of the methods developed for the total extraction of microalgal lipids require a subsequent separation for the different families (i.e neutral lipids, polar lipids) to be quantified. Moreover, most of them use toxic and expensive solvents. In the present study less toxic solvents that are widely used in the industry, such as hexane, acetone and, ethanol were tested in different orders for the extraction of microalgal biomass of different lipid composition and content (i.e. three different levels of nutritional stress). A comparison of the methods proposed by Bligh and Dyer, Folch and, Hara and Radin is also presented. The new method achieves microalgal total lipid extraction and separation of the lipid families simultaneously.

Green synthesis of biodiesel from microalgae cultivated in industrial wastewater via microbubble induced esterification using bio-MOF-based heterogeneous catalyst

Conventional homogeneous catalysts are non-biodegradable, requiring complicated downstream separation, further diminishing the overall economics. In this paper, a new heterogeneous catalyst, a metal-organic framework modified by biomaterials (Bio-MOF), complexed with an ionic liquid ([HMIM][HSO4]/Bio-MOF), has been synthesized and integrated with microbubble mediated mass transfer technology to overcome the challenges of low conversion. The ionic liquid 1-methylimidazole hydrogen sulfate provides enhanced reactivity, while the Bio-MOF provides more active sites for the reaction. Detailed kinetic analysis suggests the biodiesel production reaction occurs on the vapor/liquid (microalgae oil) interface. The results revealed a higher conversion of (molar ratio of oil: methanol =1: 15, catalyst loading = 0.5 wt% of MO, temperature = 70 ºC) 92 ± 4% was achieved in 30 min relative to acid-catalyzed biodiesel production. Along with higher reactivity and larger surface area provided by the catalysts, the unprecedented higher conversion and rate of reaction is attributed to the “local” excess of alcohol present at the interface and simultaneous removal of water from the reactor. The results of activation energy (7.9 kJ mol−1), enthalpy (4.92 kJ mol−1), entropy (−287 J mol−1), and Gibbs free energy (103.58 kJ mol−1) show that current process required less energy is required for biodiesel production. The catalyst was recycled seven times and showed high stability with little reduction in its activity over these seven runs. The study demonstrates that this newly developed catalyst provides a high reaction rate and conversion of biodiesel production from microalgae oil using a heterogeneous catalyst by integrating it with microbubble-mediated mass transfer.

Effect of ultrasonic-assisted extraction method on the oil yield and fatty acid profile of Thraustochytrium multirudimentale and Rhodotorula mucilaginosa

This study aims to examine the effect of ultrasonic-assisted extraction method on the yield of oil and the profile of fatty acid from microalga and yeast. The microalga cultivated was identified genetically as Thraustochytrium multirudimentale MAST-1 and the yeast as Rhodotorula mucilaginosa KAST-1. The oils were extracted from dried biomass by solvents using modified Bligh and Dyer (BD) method. Before the extraction, the material underwent ultrasonication, water bath immersion, and centrifugation for biomass separation from the solvent. Extracted oils were further analyzed for compositions of fatty acid using Gas Chromatography-Mass Spectrometry (GC-MS). An increase in the length of ultrasonication in the Bligh and Dyer method yielded a higher amount of oil. The cell walls disruption using ultrasonication for 60 minutes produced the highest oil yield. The BD’s extraction method was the best for yeast R. mucilaginosa KAST-1 with a yield of 46.3% oil, while the microalga T. multirudimentale MAST-1 gave only 20.6% oil. The fatty acids identified in the microalga oil were palmitic, stearic, oleic, elaidic and pentadecylic acid, while in yeast oil were palmitoleic, palmitic, pentadecylic, margaric, linoleic, elaidic, stearic and erucic acid. Linoleic acid as one of polyunsaturated fatty acid (PUFA) was detected in yeast oil.

Kinetics of Biodiesel Production from Microalgae Using Microbubble Interfacial Technology.

As an alternative to fossil fuels, biodiesel can be a source of clean and environmentally friendly energy source. However, its commercial application is limited by expensive feedstock and the slow nature of the pretreatment step-acid catalysis. The conventional approach to carry out this reaction uses stirred tank reactors. Recently, the lab-scale experiments using microbubble mediated mass transfer technology have demonstrated its potential use at commercial scale. However, all the studies conducted so far have been at a lab scale~100 mL of feedstock. To analyze the feasibility of microbubble technology, a larger pilot scale study is required. In this context, a kinetic study of microbubble technology at an intermediate scale is conducted (3 L of oil). Owing to the target for industrial application of the process, a commercial feedstock (Spirulina), microalgae oil (MO) and a commercial catalyst para-toluene sulfonic acid (PTSA) are used. Experiments to characterize the kinetics space (response surface, RSM) required for up-scaling are designed to develop a robust model. The model is compared with that developed by the gated recurrent unit (GRU) method. The maximum biodiesel conversion of 99.45 ± 1.3% is achieved by using these conditions: the molar ratio of MO to MeOH of 1:23.73 ratio, time of 60 min, and a catalyst loading of 3.3 wt% MO with an MO volume of 3 L. Furthermore, predicted models of RSM and GRU show proper fits to the experimental result. It was found that GRU produced a more accurate and robust model with correlation coefficient R2 = 0.9999 and root-mean-squared error (RSME) = 0.0515 in comparison with RSM model with R2 = 0.9844 and RMSE = 3.0832, respectively. Although RSM and GRU are fully empirical representations, they can be used for reactor up-scaling horizontally with microbubbles if the liquid layer height is held constant while the microbubble injection replicates along the floor of the reactor vessel-maintaining the tessellation pattern of the smaller vessel. This scaling approach maintains the local mixing profile, which is the major uncontrolled variable in conventional stirred tank reactor up-scaling.

Microwave-assisted epoxidized oil production from the wet microalga Nannochloropsis gaditana to obtain environmentally friendly epoxy resins

Epoxidized oils are widely used in the polymer industry to obtain biodegradable, environmentally friendly epoxy resins. This work examines solvent extraction and oil epoxidation from a wet paste of the microalga Nannochloropsis gaditana using microwave technology. An appropriate extraction solvent containing a mixture of a polar and a nonpolar solvent was selected. The results reveal that a chloroform/methanol ratio of 1:1 (v/v) promotes the high selectivity of unsaturated fatty acids of the oils for epoxidation. A central composite design was used to optimize the yield of epoxidized oils. The conditions that maximized the oxirane oxygen yield to 82.43% were as follows: temperature of 95 °C, catalyst dosage 0.25% wt, and heptane/oil mass ratio 3:4, using a formic acid/hydrogen peroxide 0.3:1.1 molar ratio.The epoxidation kinetics of microalgal oils and a mathematical model were developed. Using the least-squares method to fit the experimental data, the epoxidation rate constant found was on the order of 10−4 L mol−1 s−1 and the activation energy of 15.62 kJ/mol. Finally, the process presented some advantages due to the elimination of the drying step and the decrease in both reaction time and solvent dosage used during extraction and epoxidation.