Transesterification Of Lipids Research Articles

Fabrication of heterogeneous catalyst for production of biodiesel form municipal sludge

Sewage sludge, a semi-solid byproducts of municipal wastewater treatment processes, offers a sustainable and cost-effective feedstock for biodiesel production through the synthesis of catalytic heterogeneous catalysts. In this study, we developed a novel heterogeneous catalyst by impregnating aluminum nitrate and calcite, obtained from carbon dioxide-sequestering bacteria, onto DigSBiochar (Biochar derived from digested sewage sludge). The produced catalyst was subsequently immobilized with the lipase enzyme isolated from Bacillus sp., creating a bioactive material for the transesterification of lipids in sewage sludge. Comprehensive characterization of the biocatalysts was conducted using Energy Dispersive Spectroscopy (EDS), Fourier Transform Infrared Spectroscopy (FTIR), and Field Emission Scanning Electron Microscopy (FE-SEM). Gas Chromatography-Mass Spectrometry (GC-MS) analysis of the resulting fatty acid methyl esters (FAMEs) demonstrated that the highest yield was achieved with the enzyme immobilized on the activated heterogeneous catalyst using methanol (99 %), followed by the activated heterogeneous catalyst with methanol (96 %), and methanol with Sulfuric acid (82 %). This study underscores the potential of utilizing municipal sewage sludge as a valuable resource for producing efficient heterogeneous catalysts, thereby advancing sustainable waste management practices and promoting renewable energy production.

The potential of magnesium oxide nanoparticles (MgONPs) in the transesterification of lipids produced by Rhodotorula minuta.

The urgent need to address energy security risks and global warming has led to exploration of renewable energy sources. One such avenue is biodiesel specifically focusing on the potential of Rhodotorula minuta, a type of yeast known for producing lipids that can be used as a sustainable alternative for production of biodiesel. In the current study, this promising yeast was evaluated for its potential to produce lipids. The morphological characterization was carried out by scanning electron microscope (SEM), and intracellular detail was studied by transmission electron microscope (TEM). Changes in content and cellular biomass were monitored at time intervals with the highest biomass yield of 12.4g/l and lipid content of 6.2g/l achieved after 72h. In the present work, magnesium oxide nanoparticles (MgO NPs) were synthesized and extensively characterized through Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), Brunauer-Emmett-Teller (BET), SEM, TEM, and X-ray diffraction (XRD). By employing response surface methodology (RSM) with Box-Behnken design (BBD), optimal process conditions for transesterification could be determined. The best result achieved was a yield of 88.6% when the conditions were optimized, using methanol to oil ratio of 18:1 and 8% (w/w) amount of catalyst maintaining a reaction temperature of 55°C and allowing the reaction to proceed for 120min.

Lipid extraction and analysis of microalgae strain pectinodesmus PHM3 for biodiesel production

The current study is focused on the lipid extract of microalgae; Pectinodesmus strain PHM3 and its general analysis in terms of chemical contents. Combinations of both chemical and mechanistic approaches were applied to obtain the maximum yield of lipids which was recorded to be 23% per gram through continuous agitation using Folch solution. The extraction methods used in this study included: Bligh and Dyers method, Continuous agitation method, Extraction using Soxhlet and Acid base extraction method. Lipid quantification of ethanol and Folch solution lipid extract was performed through gravimetric methods and qualification was done through Fourier Transmission Infrared Spectroscopy (FTIR) and Gas Chromatographymass spectrometry (GC-MS). Phytochemical analysis identified other compounds in ethanol extract and the results confirmed the presence of steroids, coumarins, tannins, phenols and carbohydrates. Transesterification of lipids showed 7% per gram dry weight yield of Pectinodesmus PHM3. GC-MS studies of extracted biodiesel suggested that 72% of biofuels was in the form of dipropyl ether, ethyl butyl ethers, methyl butyl ether and propyl butyl ether. Lipid processing of acid-base extract showed that oily nature of lipid shifted to a more precipitated form which is a common observation when mixture of lipids is converted to phosphatides.

Production and Physiochemical Characterization of Biodiesel from Nile cabbage grown in Pager River, Kitgum Municipality, Northern-Uganda

Nile cabbage (Pistia stratiotes) represents a promising source of biodiesel which has been garnered due to good biomass yield. This study aims to determine the possibility for biodiesel production from Nile cabbage plants collected from a seasonal Pager River. The bio-oil extraction from Nile cabbage leaves was done using soxhlet apparatus. The biodiesel was produced by transesterification of lipids and characterized by GC-FID and the physio-chemical parameters of the produced biodiesel were also performed. The obtained results indicate that, Nile cabbage sample showed a yield of biodiesel (30.30±0.01) %. The biodiesel obtained possess the following fuel properties: density (880.00±0.00)Kg/m3, pH (5.70±0.00), saponification value (137.10±0.09) mg KOH/g, acid value (1.00±0.00) mg KOH/g, iodine value (63.41±0.01) mg I2/100g, flash point (120±0.00)℃, pour point (-6.20±0.03) ℃, colour (brown), moisture content (50.00±0.00)%, and ash content (0.003±0.00)%, and cetane number (49.53±0.05). The GC-FID analysis of the obtained biodiesel showed the presence of C16:0, C18:0, C18:1 and C18:2 as the major constituents of fatty acids (FAs) detected. Therefore, all physiochemical parameters were within the allowable limits, accept only acid value which was slightly higher than the standard limits issued by the American and European (ASTM D 6571:12 and EN 14214:2012) standards. Aquatic weeds are considered a global threat in the aquatic ecosystem, which invoked a lot of attention from the general public and the scientific community. Our findings showed that Nile cabbage biomass could give a significant yield of biodiesel, with desired fuel properties which will initiates a cleaner energy.

Alkyl carbamate ionic liquids for permeabilization of microalgae biomass to enhance lipid recovery for biodiesel production

Microalgae are potential biomass source for biodiesel production. However, their strong cell walls make efficient lipid extraction problematic. Disrupting the cell wall is a key point in enhancing lipid yield from microalgae biomass. A new type of ionic liquid (IL) has been suggested in this work as a potentially viable solvent to permeabilize the strong microalgae cell structure for the efficient extraction of lipids. Morphological changes in microalgae cells were studied before and after ionic liquid permeabilization to understand the mechanism of ionic liquid treatment. Among the three selected CO2-based alkyl carbamate ionic liquids, DIMCARP performed with the best extraction efficiency. The effects of extraction variables (temperature, time, ratio ionic liquid/Methanol, and solvent to biomass) on lipid extraction were examined via single-factor experiments coupled with response surface methodology (RSM) using a Box-Behnken design (BBD). The highest lipid yield (16.40%) was obtained after 45 min of extraction at 45 °C using a 9:1 ionic liquid to methanol and 7 mL of solvent to biomass ratio. Transesterification of lipids to make fatty acid methyl esters found that the most common fatty acids were C16:0, C18:2, and C18:3 (19.50%). The quality of the biodiesel made meets European and US standards.

Synergistic and efficient catalysis over Brønsted acidic ionic liquid [BSO3HMIm][HSO4]–modified metal–organic framework (IRMOF-3) for microalgal biodiesel production

In order to enhance catalytic active sites to improve microalgal biodiesel production, a novel efficient bifunctional catalyst was synthesized by modifying metal–organic framework (IRMOF-3) with Brønsted acidic ionic liquid (1-butylsulfonate-3-methylimidazolium bisulfate [BSO3HMIm][HSO4], IL). It was determined that IL was immobilized on IRMOF-3 framework through chemical bonding formed by an acid-base reaction between sulfonic acid group of IL and amino group of IRMOF-3. The bifunctional catalyst exhibited acid–base synergistic catalysis as well as a synergistic effect of Brønsted acid and Lewis acid, which efficiently catalyzed esterification and transesterification of microalgal lipids. The introduction of [BSO3HMIm][HSO4] on IRMOF-3 framework promoted the acidity of the catalyst from 8.91 to 10.76 mmol/g and increased strong/weak acidity ratio from 0.27 to 0.85, resulting an increased catalytic conversion efficiency of 98.2% under optimal reaction conditions. Due to the strong ionic bond, the catalyst showed good reusability with the catalytic efficiency up to 85.5% after six cycles.

An efficient heterogeneous solid acid catalyst derived from sewage sludge for the catalytic transformation of sludge into biodiesel: Preparation, characterization, and arylation process modeling

Homogeneous and heterogeneous catalysts for biodiesel production are facing challenges such as corrosion, leaching of active sites, and separation difficulties. Herein, a safe, chemically stable, and high-recoverable heterogeneous solid acid catalyst was fabricated and successfully evaluated in the catalytic transesterification of sludge-derived lipids. To this end, sludge-based granular activated carbon (SBGAC) was prepared and arylated with 4-sulfobenzenediazonium chloride in a reducing agent-free reaction. Hybrid models of the adaptive neuro-fuzzy inference system (ANFIS) with evolutionary algorithms such as the genetic algorithm (GA-FIS), particle swarm optimization (PSO-FIS), and ant colony optimization (ACO-FIS) were developed to model and optimize the empirical relationship between arylation parameters. The highest PhSO3H density (1.36 mmol/g) was obtained at 70 °C, 7.6 min arylation time, and a mass ratio of acid to SBGAC of 9.83 using the PSO-FIS model, which was ∼26% more than the value obtained without optimization. Loading 20 wt% of this catalyst in the transesterification of sludge-originated lipid at 70 °C yielded 17.34% (w/w dry sludge) biodiesel after 14 h. Coating the catalyst granules on the polystyrene grains was significantly enhanced its recoverability from the reaction mixture. Moreover, the spent catalyst exhibited good chemical stability and reusability after the ninth transesterification cycle.

MICROALGAL LIPID FROM Chaetoceros calcitrans AND ITS CONVERSION TO BIODIESEL THROUGH Ex AND In-situ TRANSESTERIFICATION

The manufacture of biodiesel from lipids can be carried out by ex and in-situ methods. The difference lies in the continuity of lipid extraction and its transesterification into biodiesel, either separately or simultaneously. The paper reported the FAME productivity from lipid Chaetoceros calcitrans that were created by both methods. The research was started by culturing Chaetoceros calcitrans in seawater media with the addition of trace elements, it produced a dry cell weight of 15 g/L on the fifth day of fermentation. The highest yield of lipid was 61.40% (w/w) obtained when the extraction was carried out from the biomass in a mixed solvent between n-hexane and 96% ethanol (1:1) assisted by a combination of hydrothermal acid and ultrasonication treatments. The transesterification of lipid that was carried out with methanol and 6% (v/v) H2SO4 catalyst for one hour at 60oC in an ex-situ process, produced FAME of 19.15% (w/w). Meanwhile, the in-situ method which joined the lipid repealing and transesterification steps simultaneously produced 21.59% (w/w) of biodiesel. The in-situ process exhibited higher FAME than the ex-situ. The main FAME component on the biodiesel of Chaetoceros calcitrans was methyl oleic (C17H33COOCH3, C18:1(Δ9 )). With insight into the cell’s pre-treatment and simultaneous process of the in-situ method, it is feasible to apply the techniques for biodiesel production in the future

Biocatalytic transesterification of algal oil employing a heterogenous methanol tolerant lipase enzyme aggregate from Bacillus mycoides strain CV18

Methanol induced lipase inactivation is the major hindrance in commercialization of enzyme catalyzed biodiesel production. Thus, methanol tolerance is highly needed for the lipase to be used in transesterification reaction. Hence, by virtue of such desirability, a methanol tolerant, extracellular lipase FDS8(L) was extracted from Bacillus mycoides strain CV18 and purified to homogeneity with 22.3 % yield. It was a non-position specific, alkaline lipase with 44 kDa of relative molecular mass and had no isoforms (confirmed by zymography). It showed optimal activity at pH 9.0 and 30 °C temperature, while stability in the pH range 7.0–10.0 and temperature upto 50 °C. Organic solvents (hexane, acetone and methanol) as well as metal ions (Mg2+, Mn2+ and Na+) had stimulatory effects on lipase activity. Lipase immobilization was done using glutaraldehyde to form cross linked lipase enzyme aggregate (CLEA) which further enhanced its stability in the presence of methanol. Owing to its methanol tolerance property, it was employed heterogeneously for catalyzing transesterification of algal lipids in methanol. The qualitative efficacy of the FDS8 lipase in converting algal lipids into biodiesel was confirmed after analyzing the hexane extracted transesterification products by TLC and FTIR spectroscopy.

A Review on the Efficient Catalysts for Algae Transesterification to Biodiesel

The depletion of fossil fuel resources and increasing environmental pollution led to a trend for using alternative, clean, green, and sustainable fuel and energy resources. To attain this aim, using biomass as an alternative resource for diesel production has been a hotspot among researchers. Biodiesel has several advantages, such as being lower toxic and more renewable, and eco-friendlier than diesel from fossil fuel resources. Several edible and non-edible bio-sources were used for the production of biodiesel from the transesterification process. Algal oil as a non-edible source is considered an abundant, low cost and green substrate for biodiesel production. Various factors such as reaction conditions and the type of catalyst affect the biodiesel production process. Different catalytic systems such as basic and acidic homogeneous and heterogeneous catalysts and biocatalysts were introduced for the process in the literature, and each proposed catalyst has its own advantages and disadvantages. For instance, in spite of the lower cost and better mass transfer of base and acid homogeneous catalysts, reaction system corrosion, non-reusability, and soap formation are serious challenges of these catalysts at an industrial scale. On the other hand, acid and base heterogenous catalysts overcame the issues of corrosion and recovery, but some matters such as mass transfer limitation, high cost, and weak performance in catalyzing both esterification of FFAs and transesterification of lipids must be taken into account. In addition, bio-catalysis as a high-cost process led to a purer product formation with less side reaction. Therefore, several significant factors should be considered for transesterification catalysts such as availability, cost, reusability, stability, mass transfer, and the possibility to manage both the transesterification of triglycerides and the esterification of FFAs, selecting a catalyst with predominant pros is viable. Here, a review of the biodiesel production from algal biomass focusing on the efficient catalyst of the process is presented.

An experimental investigation on the effect of surfactant for the transesterification of soybean oil over eggshell-derived CaO catalysts

• Nonylphenol ethoxylates was used as a co-solvent in transesterification reaction. • The use of surfactant accelerates the rate of the biodiesel production reaction. • CaO catalyst from eggshells showed high efficiency in biodiesel production. • The use of surfactant decreases the required alcohol/oil ratio. • The thermogravimetric analysis proved to be efficient for determining the FAME yield. Biodiesel is a biodegradable and renewable fuel, that generally consists of fatty acid methyl ester (FAME) produced by transesterification of lipids using methanol and a catalyst. Calcium oxide (CaO) is a heterogeneous catalyst that has been extensively studied to produce biodiesel due to its high catalytic activity. In addition, and in order to avoid mass transfer limitations that would slow down the reaction, it is also common to use a co-solvent. Thus, this work aims to evaluate the use of the surfactant Nonylphenol seven Ethoxylates (NP7EO) for the CaO-catalyzed transesterification of soybean oil. For this study, chicken eggshell was the source of calcium used to produce the CaO for the reaction. This work represents one of the few articles where transesterification was performed using a surfactant combined with a biobased and residual source of Ca. An experimental design was performed to evaluate the surfactant concentration and reaction time. Another factorial experimental design was carried out considering factors such as reaction time, catalyst concentration, and methanol-to-oil molar ratio. Ultimately, the model predicted by the experimental design was shown to be significant and the highest yield obtained after a 3 h reaction time was 98.95% with a 5 wt% catalyst loading and a 7:1 methanol-to-oil molar ratio using 1 wt% of surfactant and operated at 65 °C. The results showed that the surfactant allowed reducing the methanol-to-oil molar ratio and reaction time, which ultimately could contribute in decreasing the biodiesel production costs.

Biodiesels from non-catalytic transesterification of plant oils and their performances as aviation fuels

In accordance with the rapid growth of aviation industry, consumption of aviation fuel played a critical role as one of the major contributors of anthropogenic CO2 emission. As such, the use of aviation fuels derived from the renewable resources have gained considerable attention. To this end, this study theoretically examined the performance of aviation fuels derived from lipids in six plant oils (olive, coconut, soybean, canola, avocado, and sesame). Prior to the thermodynamic calculations, biodiesels were produced by thermally induced non-catalytic transesterification of lipids. A non-catalytic conversion platform led to conversion of plant oils into biodiesels with higher than 90% yield at 380 °C in 1 min, while the base-catalyzed reaction with KOH showed same yields after 8 h of reaction at 60 °C. An ideal gas turbine cycle of an aircraft turbojet engine was adopted to calculate the jet fuel performances of biodiesels from non-catalytic transesterification of six plant oils. As references, performances of conventional jet fuels (Jet A and JP-4) through the turbojet engine were estimated with a constant air supply. For complete combustion of fuels, biodiesels required 14 – 18% more fuel consumption rate than conventional jet fuels. The more fuel consumption rate for combustion of biodiesel led to higher engine and specific thrusts of turbojet engine, comparing to conventional jet fuels. As the result, propulsion and thermal efficiencies of biodiesels were similar with those of conventional jet fuels. Given that biodiesel is considered as a carbon neutral fuel, it was offered that jet fuels blended with biodiesel can contribute to the mitigation of CO2 emissions with no fuel performance change.

Valorization of co-products generated by argan oil extraction process: application to biodiesel production

The oil cake from argan, an available raw material in Morocco, was explored for biodiesel production. The residual lipids of roasted and unroasted argan cakes were transesterified under alkaline conditions. The best biodiesel yield (94%) was obtained after transesterification of residual lipids from roasted argan cake using a methanol:lipid ratio of 6:1 with 0.6 g of KOH per g of oil at 65 °C. Physicochemical characteristics of the oils and biodiesels, such as density, acid number, iodine, saponification and calorific value, were determined. These measured values were similar to those found with standard biodiesel and petro-diesel. Fatty acid compositions of the residual lipids and biodiesels were determined via gas chromatography, revealing 85% unsaturated fatty acid, mainly represented by oleic and linoleic acids, in these two products.

Effects of light intensity and nutrients on the lipid content of marine microalga (diatom) Amphiprora sp. for promising biodiesel production

In this research investigation, three microalgal species were screened (Pleurosigma sp., Amphora sp., and Amphiprora sp.) for lipid content before choosing the potential microalgae for biodiesel production. It was found that the lipid content of Amphiprora sp. was 41.48 ± 0.18%, which was higher than the Pleurosigma sp. (27.3 ± 0.8%) and Amphora sp. (22.49 ± 0.21%). The diatom microalga, Amphiprora sp. was isolated and exposed to a controlled environment. Two different media were prepared, and the main research was on the SiO2-NP medium as the cell wall of diatom was made up of silica. Essential growth parameters were studied such as dry cell weight and chlorophyll a content. The results revealed that Amphiprora sp. cultured in the modified medium showed a higher biomass yield and growth rate in all the analyses. In Soxhlet extraction method, biodiesel yield of Amphiprora sp. in modified medium under 24 μmol m−2 s−1 of light intensity was 81.47 ± 1.59% when using 2% of catalyst amount with 1.5:1 volume ratio of methanol/oil in 3 h reaction time at 65 °C. Results reveled that Amphiprora sp. diatom has a higher yield of oil 52.94 ± 0.42% and can be efficiently optimized with further studies with modified nanomaterial culture medium. The present research revealed the series of experiments on microalgal lipid transesterification and in future investigation different types of nanomaterials should be used in culture medium to identify the lipid production in microalgal cells.

Waste Fish Scale Derived Ferromagnetic Heterogeneous Biocatalyst (Α-Fe2O3-Β-Ca3(PO4)2) for Efficient Transesterification of Waste Silkworm Pupal Lipids into Biodiesel

This paper reports an eco-friendly, cost-effective facile route to prepare bio-derived heterogeneous magnetic biocatalysts from the waste fish scale via thermal treatment and used for efficient transesterification to produce biodiesel. The hydroxyapatite of fish scales was impregnated with the varied concentrations (10–30 wt. %) of Fe2+ precursor (FeCl2.4H2O) through the wet impregnation method and transformed into α-Fe2O3-β-TCP via calcination at 700–1000 °C. The transformation of hydroxyapatite to β-Ca3(PO4)2 impregnated with α-Fe2O3 confirmed through XRD and Raman analysis. The FTIR spectra of the prepared sample α-Fe2O3-β-TCP support its structural and chemical composition. The SEM images confirm the presence of α-Fe2O3 in the waste fish scales derived catalysts. The magnetic studies revealed the soft ferromagnetic behavior for the optimized catalysts Fe-FSC-30 with saturation magnetization 0.59 emu/g at 300 K. The magnetic fish scale catalysts was used for the transesterification of silkworm pupa lipids. The FTIR and 1H-NMR spectroscopy recognized the conversion of silkworm pupa lipids into biodiesel. The transesterification efficiency of heterogeneous magnetic biocatalysts is estimated to be ~90 % via 1H-NMR. The GC-MS identified the presence of the main constituents of SPL-biodiesel. The study demonstrated waste fish scale-derived low-cost magnetic catalysts for efficient transesterification of lipids for biodiesel production.

REACTIVE EXTRACTION SOXHLET-INTENSIFIED THE DIRECT BIODIESEL PRODUCTION OF WET SPENT COFFEE GROUND BIOMASS USING HETEROGENEOUS CATALYST

Waste spent coffee ground (SCG) has a potential lipid to use for biodiesel production. One-pot simultaneous extraction and transesterification of SCG lipid using soxhlet apparatus were developed with heterogeneous substance as the catalyst. A response surface methodology based on the Box-Behnken design experiment was established to study the effect of catalyst weight (1 – 9 wt.%), ratio methanol: hexane (1:1 – 1:5, v/v) and reaction time (30 – 90 min). The quadratic equation model generated from the design was used to predict the optimum condition and it verified by experiment. The optimum biodiesel conversion of 36% occurred using CaO as catalyst under reaction condition at the maximum level of parameters while the conversion of 90% obtained using BaO in reaction condition of catalyst weight 6.5 wt%, a ratio of 1:5 and 30 minutes reaction time. In addition, the reactive extraction soxhlet (RES) intensified the DT of wet SCG biomass required simple phase separation and evaporation of co-solvent to purify the biodiesel product.

Strategies for increasing lipid accumulation and recovery fromY. lipolytica: A review

Microbial-based biodiesel is produced by transesterification of lipids extracted from microbial cells, and is considered as a potential replacement of fossil fuel due to its advantages in reducing greenhouse gas emissions.Yarrowia lipolyticais one of the most studied oleaginous yeasts able to produce lipids under some fermentation conditions and is considered as a potential industrial host for biodiesel production. Several approaches have been evaluated to increase the economical attraction of biodiesel production fromY. lipolyticalipids. In this review, we highlighted the different strategies reported in the literature, allowing this yeast to achieve high lipid accumulation. These include metabolic engineering strategies, the use of low-cost effective substrates, and the optimization of the cultivation conditions for higher lipid productivity and less operating cost. We also summarized the most effective cell disruption technologies that improve the extraction efficiencies of lipids fromY. lipolytica.

In Situ Transesterification of Spirulina Microalgae to Produce Biodiesel Using Microwave Irradiation

The present technology of transesterification of vegetable oils to produce biodiesel, which is suited to replace petrodiesel, has economic challenges, and therefore, alternative sources are being explored. Microalgae, a renewable, third-generation biofuel resource, have the potential to become a viable feedstock due to their high oil content and environmentally friendly nature. The present study investigates the effect of microwave irradiation on the simultaneous extraction and transesterification of algae lipids to produce fatty acid methyl ester (FAME), in a batch reaction system using sulphuric acid catalyst. In situ transesterification combines the two steps of lipid extraction and transesterification into a single step. The microwave synthesis unit comprised of a 3-neck round bottom flask inside a 1300-Watt microwave oven, fitted with a quick-fit condenser and having an external stirrer. Response surface methodology (RSM) was used to analyse the influence of process variables, dry algae to methanol ratio 1 : 4 − 1 : 14 g / ml , algae biomass to catalyst ratio 1 : 0.0032 − 1 : 0.0368 wt % , and reaction time 1 − 11 min , at 500 rpm stirring rate for in situ reaction. FAME was analysed using gas chromatography (GC). The total lipid content of Arthrospira Spirulina platensis microalgae biomass was found to be 10.7 % by weight. The algae biomass also contained proteins at 51.83 % , moisture content at 7.8 % , and ash content 14.30 % by weight. RSM gave the optimum process conditions as dry algae biomass feed to methanol wt / vol ratio of 1 : 9, catalyst concentration of 2 wt % , and reaction time of 7 minutes for a maximum FAME yield of 83.43 wt % . The major fatty acid composition of FAME was palmitic 43.83 % , linoleic 38.83 % , and linolenic 19.41 % . FAME properties obtained according to European Standards (EN 14214) and American Society for Testing and Materials (ASTM D 6751) standards were as follows: flash point 16 4 o C calorific value 32,911 kJ / kg , acid value 0.475 KOH / g , viscosity 4.45 m m 2 / s , and specific gravity 0.868 . The study showed that Arthrospira Spirulina platensis microalgae lipid FAME met the biodiesel standards (EN 14214 and ASTM D 6751) and has the potential to replace petrodiesel. Microwave irradiation increased the reaction rate resulting in a reduced reaction time of 7 minutes (as compared to 8 hours for conventional heating) and therefore was found to be a superior heating mode as compared to conventional heating.

High-density biofuels production from holistic conversion of microalgal strains through energy-saving integrated approach

The commercial feasibility regarding conversion of the high-solid-loading microalgal suspensions for high-titer biofuels production is questionable owing to incomplete utilization and high processing costs. In this study, the production of multiple highly concentrated biofuels (bioethanol, higher alcohols, and biodiesel) was achieved through cost-effective integrated approach (pretreatment, serial fermentation of carbohydrate/protein, and transesterification of lipid) from highly concentrated (100 g/L) microalgal suspensions (Chlamydomonas mexicana and Chlamydomonas pitschmannii). This integrated approach attained unprecedented total conversion efficiency (48–63%) and maximum total biomass utilization (77–86%) for both the microalgal strains with high yields of bioethanol (0.48 g-ethanol/g-carbohydrate), higher alcohols (0.44 g-higher alcohols/g-protein), and biodiesel (0.82–0.89 g-biodiesel/g-lipid) at suspensions of 100 g/L. Transmission electron microscopy was employed to visualize the changes in the intercellular morphologies before and after serial fermentations. Thus, this study demonstrates a cost-effective and energy-saving integrated approach for the holistic conversion of high-solid-loading microalgal biomass to produce high-density biofuels with minimum waste generation.

Quantitative study on lipid productivity of Euglena gracilis and its biodiesel production according to the cultivation conditions

Biodiesel is a carbon neutral liquid fuel that is derived from transesterification of lipids in biomass. Microalgae could be a promising raw feedstock for biodiesel production thanks to high lipid content in line with the rapid carbon fixation capability. Nonetheless, lipid productivity from microalgae is sensitive to microalgal species and cultivation conditions. Hence, to seek cultivation parameters maximizing lipid productivity, Euglena gracilis (E. gracilis) was kept under the controlled conditions as a case study. Non-catalytic transesterification was also adopted for quantitative/qualitative analyses of lipid in E. gracilis due to its analytical reliability. E. gracilis was cultured in the aerobic condition for 7 d, and the cultivation mode was changed into the anaerobic condition for 3 d to experimentally confirm wax ester fermentation mechanisms. The lipid content in E. gracilis reached up to 24.81 wt% (dry basis) under the heterotrophic condition, which was in good agreement with the wax fermentation mechanism. It was concluded that the high dose of nutrients (glucose, nitrogen, and phosphorus) under the oxygen-free environment led to a favorable condition for lipid accumulation. Nevertheless, this study offered that lipid productivity in 6 d (0.131 g lipid L−1 d−1) under aerobic condition was higher than that in 10 d (0.092 g lipid L−1 d−1) under anaerobic condition due to substantial carbon loss arising from the wax ester fermentation stage under the anaerobic condition.