Fatty Acid Methyl Ester Content Research Articles

Box–Behnken optimization of biodiesel production using trisodium phosphate catalyst from monazite ore processes

AbstractTrisodium phosphate (TSP) is a non‐toxic waste obtained from alkaline cracking as part of the processing of monazite ore. After simple purification, TSP can be utilized in many applications; however, it is used as a catalyst in this study. It is characterized using Thermogravimetric analysis , X‐ray diffraction analysis, Brunauer‐Emmett‐Teller, and Temperature‐programmed desorption of carbon dioxide and optimized in the transesterification reaction. After recrystallization and calcination at 350 °C for 0.5 h, the form of the TSP was tetragonal, with a 2.61 m2/g surface area and 537.4 x 10‐6 mol/g basic sites. Trisodium phosphate can therefore be utilized effectively as a solid base catalyst for the transesterification of palm oil. Three biodiesel production parameters were investigated: the methanol to oil molar ratio (6:1–24:1), catalyst concentration (1–10%), and reaction time (30 to 240 min). The experiments were designed using the Box–Behnken response surface method. As a result, the optimum conditions for biodiesel production are a 22:1 methanol to oil molar ratio, 4% catalyst concentration, and 200 min reaction time. The optimal fatty acid methyl ester (FAME) content is 99.79%, with an error between actual and predicted FAME of 0.21%. © 2023 Society of Industrial Chemistry and John Wiley & Sons Ltd.

Enhancing Lipid Production of Chlorella sp. by Mixotrophic Cultivation Optimization

Mixotrophic microalgal cultivation can utilize CO2 and organic carbon sources. This study optimized the cultivation nitrogen source (peptone, urea, yeast extract, NH4Cl, (NH4)2SO4, NH4NO3, NaNO3 and KNO3), carbon combination (glucose, glycerol, sucrose), (NH4)2SO4 nitrogen source and pH (6–11) in a local microalgae species with three characteristics (high pH-resistant, high growth rate and high lipid content). Chlorella sp. G3H3-1-2 biomass production and lipid accumulation were estimated using the fatty acid methyl esters (FAMEs) concentration. The Chlorella sp. G3H3-1-2 FAME content was strongly influenced by the carbon, nitrogen sources and pH variations. The pH ranged from 6.0 to 8.0, which produced the highest specific growth rate of 1.22 day−1 for Chlorella sp. G3H3-1-2 while using glucose as the single carbon source. However, the highest total FAMEs content of 59% in the Chlorella sp. G3H3-1-2 biomass of 1.75 g/L was obtained while using the combination of 1 g-glucose/L as the carbon source and 0.2 g-(NH4)2SO4/L as the nitrogen source at the high pH value of 10.

Urban sewage sludge valorization to biodiesel production: Solvent-free lipid recovery through adsorption on used 3 Ply Safety Face Masks

The use of urban sewage sludge as the feedstock of lipids to produce biodiesel is a topic of great interest and potential. However, the extractive step, conventionally operated with organic solvents, makes this use unfeasible and with a high environmental impact. In this work, for the first time, the solvent-free recovery of lipids from sewage sludge was studied through adsorption onto non-polar polymeric materials (Spunbonded nonwoven Polypropylene (s-nwPP)). After being immersed in sedimented sewage sludge (TS: 6.9 wt%), s-nwPP sheets were easily separated, dried and analyzed: sewage sludge’s lipids were preferentially adsorbed onto the polymeric surface. Free fatty acids (FFAs) were the dominant species and were recovered from s-nwPP sheets through acidic methanol in a separated reactive washing step as fatty acid methyl esters (FAMEs) A crude product was obtained through this sequence of adsorption and reactive desorption operations, with a FAMEs content of over 55 wt%. After preliminary investigations on commercial s-nwPP sheets, 3 Ply Safety Face Masks were also positively tested. pH, weight ratio polymer/wet sludge (R) and temperature were the parameters optimized: operating at 343 K under acidic conditions (pH of sludge<2), with an R equal to 6%, a total FFAs recovery yield of 70% as FAMEs was already achieved after two adsorption cycles. A preliminary evaluation of the economic feasibility demonstrated that used PP surgical facial masks allow the recovery and generation of crude biodiesel from sewage sludge at a very reasonable price with minimal environmental impacts.

Density Measurements and PC-SAFT Modeling for Beef Tallow Fatty Acid Methyl Esters (FAME Mixture) + Alkane up to 70 MPa

Biodiesel is mainly constituted by fatty acid alkyl esters, and the effect of adding alkane compounds is of great importance in order to analyze the changes in the thermophysical properties under high pressure that is of relevance in diesel engines. This work is aimed at the study of density behavior of two systems formed by beef tallow fatty acid methyl esters (FAME mixture) + alkane (decane or dodecane) in the temperature range of 303–393 K and in the pressure range of 0.2–68.29 MPa. Experiments were carried out by means of two vibrating tube densimeters with an expanded uncertainty in density of 0.7 kg·m–3. Transesterification of waste beef tallow by using methanol at supercritical conditions was used to obtain biodiesel. The FAME mixture was constituted by methyl tetradecanoate, methyl hexadecanoate, methyl octadecenoate, and methyl (Z)-octadec-9-enoate. Density behavior was correlated using the Tammann–Tait equation and modeled with the perturbed-chain statistical associating fluid theory (PC-SAFT) equation of state. Density correlation deviations using the Tammann–Tait equation were found to be less than 0.05% and 4.15 kg·m–3 for the average absolute deviation (AAD) and standard deviation (STD), respectively. The PC-SAFT modeling yielded an AAD = 0.11% and an STD = 1.15 kg·m–3. The behavior for density and the derived thermodynamic properties were explained in terms of the fatty acid methyl ester content.

Biodiesel Production Catalyzed by Lipase Extract Powder of Leonotis nepetifolia (Christmas Candlestick) Seed

This work aimed to evaluate the ability of lipase extract powder obtained from Leonotis nepetifolia seed for enzyme-catalyzed biodiesel production using Leonotis nepetifolia oil, commercial olive oil, and waste cooking oil as substrates. The lipase extract powder showed an enzymatic activity and hydrolysis percentage of 24.7 U/g and 21.31%, respectively, using commercial olive oil as a reference. Transesterification reaction conditions were 40 g of substrate, 34 °C, molar ratio oil: methanol of 1:3, lipase extract powder 20 wt%, phosphates buffer (pH 4.8) 20 wt%, and a reaction time of 8 h. Transesterification yields of 74.5%, 71.5%, and 69.3% for commercial olive oil, waste cooking oil, and Leonotis nepetifolia oil were obtained, respectively. Biodiesel physicochemical parameters were analyzed and compared with the international standards: EN 14214 (European Union) and ASTM D6751 (American Society for Testing and Materials). The biodiesel’s moisture and volatile matter percentages, iodine index, cooper strip corrosion, and methyl esters content conformed to the standards’ specifications. The fatty acid methyl ester content of the vegetable oils showed the presence of methyl oleate after enzyme-catalyzed transesterification. This study reveals that biodiesel production catalyzed by lipase extract powder from Leonotis nepetifolia could be a viable alternative, showing that transesterification yields competitive results.

Spent coffee grounds and orange peel residues based biorefinery for microbial oil and biodiesel conversion estimation

A consolidated biorefinery was developed using spent coffee grounds (SCGs) and orange peel residues (OPR) to produce microbial oil and value-added co-products. Coffee oil and antioxidant-rich extracts were initially extracted from SCGs. Free sugars and pectin-rich extracts were obtained from OPR. Microbial oil production was evaluated using various oleaginous yeast strains cultivated in commercial carbon sources. Microbial oil production was demonstrated in 30 L bioreactor scale using combined OPR-SCGs hydrolysate resulting in 56.7% (w/w) intracellular lipid accumulation and 0.32 g/(L∙h) productivity, corresponding to 68.1 g microbial oil production per 1 kg SCGs and 360 g OPR. Principal Component Analysis has been carried out to assess the similarity of microbial oil produced in this study and literature-cited oils considering the fatty acid methyl ester content. The biodiesel properties estimated based on predictive equations showed that they generally conformed with the limits set by European standards.

Effects of feast-famine nutrient regimes on wastewater algal biofuel communities.

Microalgae accumulate lipids in response to nutrient deprivation, and these lipids are a biodiesel fuel stock. Algal cultivation with secondary wastewater effluent is one proposed platform for biofuel production, which provides nutrients to algae while further polishing wastewater effluent. Algal bioreactors were tested using a feast-famine feeding regiment in simulated secondary wastewater effluent to evaluate the effects on lipid content and algal community structure. Algal polycultures were inoculated into reactors fed with synthetic secondary wastewater effluent at pH 7.5 and 9 and operated under a feast-famine nutrient (N, P, and BOD) supply regime in sequencing batch reactors. Fatty acid methyl ester contents of the reactors were assessed, which showed a decrease in lipid content after the feast-famine cycling (from 12.2% initially to 5.2% after four cycles at pH 9). This decrease in lipid content was not correlated with an increase in carbohydrate storage within biomass, nor an increase in bacterial biomass abundance relative to algal biomass in the reactors. The eukaryotic microbial communities from reactors operated at pH 9 diverged from reactors operated at pH 7.5 during cycling, with the pH 9 reactors becoming dominated by a single Operational Taxonomic Unit aligning to the Scenedesmus genus. These results suggest that high pH and feast-famine nutrient cycling may select for a less diverse algal community with a lower lipid content within a secondary wastewater polishing scheme.

Integrating biological and chemical CO2 sequestration using green microalgae for bioproducts generation

Microalgae cultivation is considered an attractive negative emission technology (NET) due to its ability to remove carbon dioxide (CO2) from the atmosphere as well as from flue gases. Moreover, some microalgae can uptake dissolved carbon in the form of bicarbonate (HCO3-) and grow well by removing nutrients from various wastewater effluents without competing with freshwater resources. Conventional carbon mineralization is another NET where carbon is fixed into carbonate minerals such as calcite (CaCO3), magnesite (MgCO3), nesquehonite (MgCO3-3H2O), and nahcolite (NaHCO3), which can be reused in various applications such as construction and cosmetics, and in this case, to supply carbon to microalgae. Previous initial laboratory studies demonstrated the possibility of using metastable carbonates as a source of carbon for biomass growth of the freshwater microalga Scenedesmus obliquus. In this study, we present results from an experimental and modeling work where 100 L open raceway reactors were used to grow an algae polyculture using industrial nitrogen-rich wastewater. In addition, carbonates such as MgCO3-3H2O and sodium carbonate (Na2CO3) were added to the ponds to primarily buffer the pH and maintain it within the acceptable algae physiological values and to provide extra carbon to the cultures. Cultures using BG-11 growth medium and without addition of carbonates were run as controls. Continuous online monitoring of pH, temperature, and dissolved oxygen was performed while nutrients content and dry weight of algae culture were measured offline daily. A mathematical model coupled with geochemistry was implemented to describe the overall process of algae growth, carbonate dissolution, and solution composition. Biomass harvested from the raceway reactors was concentrated and oil and fatty acid methyl esters (FAME) content were determined. Results showed that biomass and oil content obtained were comparable to controls, indicating a successful metabolic-based pH control by the addition of carbonates in the ammonium-based media. Furthermore, FAME analysis revealed different profiles depending on the source of carbon used. Overall, this study suggests that integrating both types of NET strategies can contribute to the reduction of carbon emissions while producing biomass that can be further processed to generate a variety of bioproducts.

Enhanced Bioconversion of Methane to Biodiesel by Methylosarcina sp. LC-4

The conversion of methane into liquid biofuels using methane-consuming bacteria, known as methanotrophs, contributes to sustainable development, as it mitigates the problem of climate change caused by greenhouse gases and aids in producing cleaner and renewable energy. In the present research, an efficient methanotroph, Methylosarcina sp. LC-4, was studied as a prospective organism for biodiesel production using methane. The methane uptake rate by the organism was enhanced 1.6 times and 2.35 times by supplementing LC-4 with micronutrients, such as copper and tungstate, respectively. This unique ability of the isolated organism enables the deployment of methanotrophs-based processes in various industrial applications. A Plackett–Burman statistical (PBD) design was used to quantify the role of the micronutrients and other media components present in the nitrate minimal salt media (NMS) in biomass and fatty acid methyl esters (FAME) yields. Nitrate, phosphate, and tungstate had a positive effect, whereas copper, magnesium, and salinity had a negative effect. The modified NMS media, formulated according to the results from the PBD analysis, increased the FAME yield (mg/L) by 85.7%, with the FAME content of 13 ± 1% (w/w) among the highest reported in methanotrophs. The obtained FAME consisted majorly (~90%) of C14–C18 saturated and monounsaturated fatty acids, making it suitable for use as biodiesel.

Fusion-Assisted Hydrothermal Synthesis and Post-Synthesis Modification of Mesoporous Hydroxy Sodalite Zeolite Prepared from Waste Coal Fly Ash for Biodiesel Production

Increases in biodiesel prices remains a challenge, mainly due to the high cost of conventional oil feedstocks used during biodiesel production and the challenges associated with using homogeneous catalysts in the process. This study investigated the conversion of waste-derived black soldier fly (BSF) maggot oil feedstock over hydroxy sodalite (HS) zeolite synthesized from waste coal fly ash (CFA) in biodiesel production. The zeolite product prepared after fusion of CFA followed by hydrothermal synthesis (F-HS) resulted in a highly crystalline, mesoporous F-HS zeolite with a considerable surface area of 45 m2/g. The impact of post-synthesis modification of the parent HS catalyst (F-HS) by ion exchange with an alkali source (KOH) on its performance in biodiesel production was investigated. The parent F-HS zeolite catalyst resulted in a high biodiesel yield of 84.10%, with a good quality of 65% fatty acid methyl ester (FAME) content and fuel characteristics compliant with standard biodiesel specifications. After ion exchange, the modified HS zeolite catalyst (K/F-HS) decreased in crystallinity, mesoporosity and total surface area. The K/F-HS catalyst resulted in sub-standard biodiesel of 51.50% FAME content. Hence, contrary to various studies, the ion exchange modified zeolite was unfavorable as a catalyst for biodiesel production. Interestingly, the F-HS zeolite derived from waste CFA showed a favorable performance as a heterogeneous catalyst compared to the conventional sodium hydroxide (NaOH) homogeneous catalyst. The zeolite catalyst resulted in a more profitable process using BSF maggot oil and was economically comparable with NaOH for every kilogram of biodiesel produced. Furthermore, this study showed the potential to address the overall biodiesel production cost challenge via the development of waste-derived catalysts and BSF maggot oil as low-cost feedstock alternatives.

Batch-to-Batch Adaptive Iterative Learning Control-Explicit Model Predictive Control Two-Tier Framework for the Control of Batch Transesterification Process.

To harness energy security and reduce carbon emissions, humankind is trying to switch toward renewable energy resources. To this extent, fatty acid methyl esters, also known as biodiesel, are popularly used as a green fuel. Fatty acid methyl esters can be produced by a batch transesterification reaction between vegetable oil and alcohol. Being a batch process, fatty acid methyl esters production is beset with issues such as uncertainties and unsteady state behavior, and therefore, adequate process control measures are necessitated. In this study, we have proposed a novel two-tier framework for the control of the fatty acid methyl esters production process. The proposed approach combines the constrained batch-to-batch iterative learning control technique and explicit model predictive control to obtain the desired concentration of the fatty acid methyl esters. In particular, the batch-to-batch iterative learning control technique is used to generate reactor temperature set-points, which is further utilized to obtain an optimal coolant flow rate by solving a quadratic objective cost function, with the help of explicit model predictive control. Our simulation results indicate that the fatty acid methyl esters concentration trajectory converges to the desired batch trajectory within four batches for uncertainty in activation energy and six batches for uncertainty in both inlet concentration of triglyceride and in activation energy even in the presence of process disturbances. The proposed approach was compared to the heuristic-based approach and constraint iterative learning control approach to showcase its efficacy.

Application of thermogravimetric analysis method for the characterisation of products from triglycerides during biodiesel production

In this present work, thermogravimetric analysis (TGA) was used to study the thermal degradation of a range of lipids and lipid-derived compounds associated with the production of biodiesel. Thereafter, the procedure was used to successfully quantify the compounds of three process streams from a biodiesel plant. Relevant organic chemicals involved in biodiesel production chemistry, including glycerol, oleic acid (fatty acid), palmitic acid (fatty acid), rapeseed oil (model triglyceride) and fatty acid methyl esters (FAMES) have been studied to determine their volatilisation/thermal degradation patterns. The developed method was then applied for the quantitative characterisation of three samples from a 3-stage biodiesel production plant, including two in-process samples and the final biodiesel product. The method was able to clearly distinguish between two main sets of compounds namely, early - mid volatiles (glycerol, fatty acids and fatty acid methyl esters) and late volatiles (incompletely converted and unreacted triglycerides). In addition, the FAMES in the industrial samples were extracted into petroleum ether and analysed by gas chromatography - mass spectrometry (GC/MS), with good agreement between the two analytical methods. For instance, GC/MS analysis showed that the three industrial samples contained 31.2 ± 0.1 wt%, 60.6 ± 0.2 wt% and 91 ± 0.53 wt% of FAMES, respectively. Similarly, the TGA method gave the FAMES contents of the three samples as 33.9 ± 0.4 wt%, 57.8 ± 0.2 wt% and 85.3 ± 0.52 wt%. This study shows that TGA is a fast and simple method for accurately monitoring the triglyceride conversion stages and the purity of the final product during biodiesel production, without the need for extensive sample preparations and expensive standard solutions.

Electrolytic transesterification of waste cooking oil using magnetic Co/Fe–Ca based catalyst derived from waste shells: A promising approach towards sustainable biodiesel production

Biodiesel production is a promising approach to producing renewable liquid fuel and disposing of waste cooking oil (WCO). While the high energy consumption during the conventional thermal transesterification process and the difficulty of reusing the transesterification catalyst are two important factors affecting its development. In this research, biodiesel production by electrolytic transesterification of WCO using reusable magnetic waste shells derived Co/Fe–Ca based catalysts were evaluated. Catalysts were prepared by one-step hydrothermal method. Their properties were characterized by XRD, SEM, XPS, etc, catalytic performances were investigated, and catalytic mechanisms were also explored. Response surface methodology (RSM) based on the Box-Behnken design (BBD) approach was used to optimize the electrolytic transesterification parameters and investigate the interactions of independent parameters. An optimal Fatty acid methyl ester (FAME) content of 92.12% was obtained under a 12:1 methanol to oil molar ratio, 0.25 wt% catalyst dosage, and 29 V electrolytic voltage for 50 min at room temperature. The conversion of WCO is more dependent on electrolytic voltage as compared to the other parameters. And the reaction time has been significantly decreased, energy efficiency was effectively improved compared to conventional thermal catalytic transesterification. Moreover, the WCO biodiesel properties were measured and they all met the ASTM standard. It's hoped that the results of this work could promisingly benefit the sustainable biodiesel production and disposal of WCO.

Study the Stable Diatomite-supported Catalyst for Biodiesel Production

The stable of natural diatomite supported by potassium hydroxide (KOH) as catalysts were synthesized for biodiesel production. A heterogeneous base catalyst prepared by impregnating KOH onto diatomite was also used to synthesize biodiesel from palm oil. All samples have been thoroughly characterized by Wavelength Dispersive X-ray Fluorescence (WDXRF), X-ray diffraction (XRD), N2 adsorption/desorption, Scanning electron microscopy (SEM), Energy dispersive spectrometer (EDS), and Temperature-programmed desorption of carbon dioxide (CO2-TPD). The XRD, XRF, and SEM results confi rm that adding KOH to diatomite results in structural change. The SiO2 and K2O phases form in the diatomite structural matrix during impregnation and the total basicity amount of this compound promotes the transesterifi cation process. A maximum fatty acid methyl ester (FAME) content of 84.56% was obtained. The reaction conditions were as follows: molar ratio of oil to methanol 1:9, catalyst loading 5 wt%, reaction time 2 h, and reaction temperature 75 °C. This work provides a possible new method for converting KOH from a homogeneous to a heterogeneous catalyst (Diatomite/KOH) that may show stable reusability, avoiding the separation and pollution problems in the environment.

Real textile industrial wastewater treatment and biodiesel production using microalgae

Microalgae are promising feedstocks capable to simultaneously treat wastewater and produce biodiesel. The focus current studyis the treatment of real textile wastewater (RTWW) and successive biodiesel production using microalgae (Chlorella vulgaris). Cultivation was carried out in unsterilized 100% (without dilution) and diluted (25%, 50%, 75%) RTWW. Microalgae cultivation in defined media (BG-11) was set as a control. In results, 50% dilution showed the highest decolorization efficiency (99 ± 0.13%), COD removal (82%), and Fatty Acid Methyl Esters (FAMEs) content (32.62 mg g−1 of biomass). Cultivation was carried out in mixotrophic and heterotrophic conditions to improve microalgae performance. Mixotrophic cultivation showed 99 ± 0.29% decolorization, 94% COD removal, and 61.65 mg g−1 of biomass as FAMEs, which was higher (p < 0.05) than the heterotrophic condition. FAME content and COD removal in mixotrophic conditions were higher (p < 0.05) than in photo-autotrophic conditions; however, there was no significant difference (p > 0.05) in the decolorization efficiency. Thus, it turned out that 50% diluted RTWW under mixotrophic conditions was the most suitable choice to achieve high treatment performance and the FAMEs yield. This study demonstrates that RTWW could be used as a microalgae feedstock without sterilization and less freshwater addition (50% of RTWW). Thus, it can be considered a promising feedstock for economical biodiesel production.

Development of a zeolite supported CaO derived from chicken eggshell as active base catalyst for used cooking oil biodiesel production

Herein, used cooking oil (UCO) was upgraded to fatty acid methyl ester (FAME) via methanolysis process using zeolite based eggshell (ZE/ES) composite catalyst. The ZE/ES catalyst was prepared using wet impregnation technique followed by calcination at different temperatures (700–900 °C), and its properties were evaluated by various characterization techniques (BET, TGA/DTA, FTIR, CO2-TPD, XRD, SEM and surface basicity). Optimization of methanolysis of UCO was studied using central composite design. Under the optimum transesterification conditions (at 69.1 °C for 238.8 min using methanol/UCO molar ratio of 9.7:1 with 2.1 wt% catalyst dosage), the maximum FAME content was 93.7% when composite catalyst synthesized by loading 2 g of zeolite with 5 g of eggshell and calcined at 800 °C (2ZE/ES-800) was utilized. The remarkable performance of 2ZE/ES-800 could be attributed to its high basic strength (1181.1 μ mol/g) and dominance of the CaO on its surface. Reusability study showed that the 2ZE/ES-800 catalyst could be reused for five successive cycles with no significant decrease in catalyst activity.

Effect of Processing Parameters to The Fish Oil from Fish Waste Via Modified Soxhlet Extraction

The oil production and fatty acid methyl ester (FAME) contents of fish waste were studied. Solvent, temperature, and extraction time were the processing parameters involved. The oil and FAME were extracted using a modified soxhlet extraction method. The best solvent for fish oil extraction was found to be ethanol, which yielded 49.0%, followed by ethanol:heptane (1:1), methanol:heptane (1:1), and methanol. The oil extract composition contained a high yield of oleic acid (C18:1), ranging from 42% to 66%. Followed by palmitic acid (C16:0), palmitoleic acid (C16:1), and stearic acid (C18:0). According to the statistical model obtained, at the 95% confidence level, extraction time had a significant effect on both oil and oleic acid yield (C18:1). These results demonstrated that a high oleic acid fraction can be obtained from fish waste with ethanol, implying that there is a high potential for cost-effective biofuel production.

Attached microalgae converting spent coffee ground into lipid for biodiesel production and sequestering atmospheric CO2 simultaneously

The impacts of simultaneous exposures of arbitrary light intensities and photoperiods on attached Chlorella vulgaris microalgal growth onto spent coffee ground (SCG) were studied, and subsequently optimized using Response Surface Methodology (RSM) tool. The statistical analysis revealed the optimum light intensity and photoperiod were achieved at 100 μmol/m2s and 20:4 dark:light hours/cycle, respectively, producing microalgal density of 0.358 g/g and lipid productivity of 16.8 mg/Lday. The biodiesel yielded from the optimum condition possessed high cetane number and oxidative stability due to the high saturated fatty acid methyl esters (FAME) content of 63.7 %. In fact, the major FAME compositions ranged within C16 to C18 which were favourable for quality biodiesel production. Furthermore, the viability of SCG to serve as a carbon source was also evidenced by the high productivities of microalgal protein and carbohydrate at 94 and 168 mg/L day, respectively. The capability of attached microalgal cultivation in sequestering atmospheric CO2 was finally unveiled, with high CO2 capture rate being recorded at 9.38 mg/L h. Accordingly, growing attached microalgae onto SCG was recognized as an alternative approach for sustainable CO2 reduction, while producing green diesel to assuage the global warming phenomenon.

Cold stress stimulates algae to produce value-added compounds

Two cold-tolerant microalgae, Chlorella vulgaris and Scenedesmus sp., were grown at 22 and 5 °C. At the lower temperature, the microalgae showed substantial biochemical and morphological changes. The soluble sugar profile in response to low-temperature cultivation was very different in the two strains. C. vulgaris increased both the sucrose and raffinose family oligosaccharides (RFOs) content at 5 °C while Scenedesmus sp. drastically reduced the sucrose content. Both strains increased the total fatty acid methyl ester (FAME) content when grown at 5 °C. However, the FAME profiles were very different: C. vulgaris mainly increased C18:1 and less so C18:3, while Scenedesmus sp. decreased C18:1 but greatly increased C18:3. The morphology of C. vulgaris changed slightly at the lower temperature, while Scenedesmus sp. showed substantial changes in the size and shape. Low temperature triggered the synthesis of unsaturated fatty acids that are essential for human nutrition.

Flow and crystallization of saturated fatty acid methyl esters and their binary mixtures

AbstractDemand for biodiesel has increased due to being a more environmentally‐friendly fuel. Cold weather operation of biodiesel is challenging due to fatty acid methyl ester (FAME) content in biodiesel. Saturated FAMEs crystallize at relatively high temperatures, increase the viscosity of biodiesel, and can clog fuel lines. Here, several factors altered crystallization temperature (CT) of FAMEs, including composition, shear rate, and cooling rate. The crystallization of pure and binary mixtures of methyl palmitate, methyl myristate, and methyl stearate were studied under shear flow and static conditions. Static phase CTs of pure methyl palmitate, methyl myristate, and methyl stearate were 26, 14, and 35°C, respectively. In binary mixtures, CTs were depressed up to 7°C, which agreed with freezing point depression theory. Increasing shear rate up to 100 s−1 decreased CT by 2°C compared to static conditions. Decreasing cooling rate from 1 to 0.1°C/min increased CT less than 2°C. Overall, FAME composition altered CT more than shear flow or cooling rate for pure and binary mixtures of three FAMEs.