Bioremediation and Biofuel Production Potential of Microalgae and Cyanobacteria from Lake Xochimilco

Comparative study on saturated and unsaturated fatty acid methyl esters (FAME) composition in biodiesel production from waste soybean, sunflower, and canola oils

Possible interactions of insoluble organic geopolymers (kerogen) with organic compounds in the aquatic environment—I. Interaction with fatty acid methyl esters

Biodiesel is viewed as the alternative to petroleum diesel, but its poor low-temperature performance constrains its utilization. Cloud point (CP), the onset temperature of thermal crystallization, appropriately shows the low-temperature performance. The effective way to reduce CP is to remove saturated fatty acid methyl esters (FAMEs). Compared to current methods, this work describes an extraordinary approach to fractionating FAMEs by forming solid urea inclusion compounds (UICs). Urea inclusion fractionation reduces the CPs by removing high melting-point linear saturated FAME components. Urea inclusion fractionation in this study was performed under various processing conditions: mass ratios of urea to FAMEs and solvents to FAMEs, various solvents, FAMEs from various feedstocks, and processing temperatures. Supersaturation of urea in the solution is the driving force, and it significantly affects yield, composition, CP, separation efficiency, and selectivity. Through a single urea inclusion fractionation process, FAMEs, except palm oil FAMEs, resulted in CP reduction ranging from 20 to 42 oC with a yield of 77–80% depending on the compositions. CP of palm oil FAMEs could reach as low as -17 oC with a yield of 46% after twice urea inclusion fractionation. According to the model prediction, the cetane number after urea inclusion fractionation decreased about 0.7–2 but was still higher than the minimum biodiesel requirement. Oxidation stability after urea inclusion decreased according to the proposed model, but this can be mitigated by adding antioxidants. Emission evaluation after urea inclusion fractionation indicated decreased hydrocarbons, carbon monoxide, and particulate matter. However, it resulted in the increasing emission of nitrogen oxides.

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

In this paper, natural sunflower seed oil was used as the raw material to extract mixed fatty acids with potassium hydroxide-methyl alcohol solution, and then benzene and methanol were added for methylation reaction, and finally the saturated and unsaturated fatty acid methyl ester were separated by urea encapsulation method. The optimal reaction temperature of the mixed fatty acid extraction process, the optimal dosage ratio of urea to mixed fatty acid methyl ester and the optimal freezing temperature in the urea encapsulation process were explored. Fourier transform infrared spectrometer (FT-IR) and GC-MS were used to analyze. The results show that after methyl esterification of the extracted fatty acids, the separation efficiency of the saturated fatty acid methyl esters by the urea encapsulation method was extremely high, and the content of the unsaturated fatty acid methyl ester in the filtrate was up to 99.67%, which made a solid foundation for further demethylation to prepare unsaturated fatty acids.

Biodiesel from saturated and monounsaturated fatty acid methyl esters and their influence over noise and air pollution

Effect of nonionic surfactants on the low temperature winterization separation of fatty acid methyl ester mixtures

The eluotropic strength of binary mobile phases was calculated for three homologous series of cis, trans, and cis-cis unsaturated fatty acid methyl esters (FAMEs). Binary mobile phases with chloroform, dichloromethane, or tetrahydrofuran as strong solvent and methanol or acetonitrile as weak solvent were tested. The volume fraction of strong solvent in the binary phases was between 0.3 and 0.8. Curves of eluotropic strength versus volume fraction of strong solvents showed similar trends to previously published results for saturated homologues. Correlation coefficients of the plots of eluotropic strength values for saturated versus unsaturated FAMEs were close to 1.0. Therefore these similarities validate the model of eluotropic strength previously established with saturated FAMEs as relevant for unsaturated FAMEs. The separation factors between cis and trans homologues always showed elution of the cis before the trans homologue. The difference in retention is due primarily to the geometry of the molecule. The retention is lowered more by the addition of a first carbon double bond than by the addition of a second one, independently of the mobile phase composition.

Microalgae are well considered to be promising feedstocks for biodiesel production. Microalgae can be grown under different types of cultivation conditions and their biomass has tremendous potential to be used as biofuel feedstock and for other applications such as feed, food, cosmetics, pharmaceutical etc. Despite the many benefits and the significant development in the field of microalgal biodiesel production, there are several challenges including high cultivation cost and developing efficient downstream processing methods. The biomass production cost is high, which significantly hinders the use of microalgae as a feedstock. Most of the available literature is focused on upstream, single strain and single product strategy, where mainly algal lipids are used for biofuel production. Hence, for improving the sustainability of the algal biofuel production processes and related process economics, a multiple applications approach using integrated biorefinery and exploiting microalgae for environmental benefits is required. To explore the microalgal biorefinery concept it is vital to understand the various cultivation conditions and applications of biomass in different sectors. There are various strategies, which have potential to make algal biofuel technologies more economically feasible and environmentally sustainable. Use of alternative culture media, improving the biomass production and the efficiency of downstream processing (drying, cell disruption, lipid extraction etc.) algal biofuel technology economical. Utilizing lipid-extracted algae (LEA) for energy and aqua feed application will maximize overall economic return and will leave minimal residues as by-product. The major focus of this thesis was to utilize LEA as substrate for biomethane production and protein source in aquaculture feed. However, effect of preceding steps such as microalgae cultivation, biomass drying and cell disruption on major metabolites extraction was also studied. Microalgae were cultivated in different medium (domestic wastewater and BG11) and their biomass yields and biochemical composition (lipid, protein and carbohydrate) were compared. Different drying and cell disruption techniques were employed for lipid extraction and their effect on lipid, protein and carbohydrate yields were evaluated. The yield of major metabolites on whole cell and LEA were also compared. Suitable solvent systems were selected for optimum lipid extraction from wet and dry biomass with minimal toxic effect on LEA metabolites so that LEA can be further used for biomethane and aquaculture feed production. The choice of microalgae at large scale depends upon the number of factors such as their adaptability to large-scale cultivation, biomass production, major metabolites content, robustness towards the open system cultivation and contamination. In this study, S. obliquus and C. sorokiniana were cultivated in wastewater and BG11 medium at laboratory scale. Both strains are indigenous to KwaZulu-Natal. C. sorokiniana showed lower biomass and major metabolites (lipid, protein and carbohydrate) production at large scale compared to S. obliquus. Considering better adaptability to open cultivation, high biomass and metabolites yields, S. obliquus strain was selected for the LEA application study. Microalgae species, C. sorokiniana and S. obliquus were cultivated on BG11 and using different ratios of raw domestic wastewater and post-chlorinated wastewater as nutrient media. The cultivation of S. obliquus and C. sorokiniana showed biomass yield of 1.2-3.5 and 0.78-1.8 g L-1 in BG11 medium, respectively. While biomass yield observed in wastewater was 0.59-1.59 g L-1 for S. obliquus and 0.67-1.45 g L-1 for C. sorokiniana. The higher biomass yield in BG11 medium attributed to the higher nutrient contents in this medium compared to wastewater. The lipid contents for S. obliquus and C. sorokiniana were 20 and 16.5% dry cell weight (DCW), respectively when grown using BG11 medium. While increases in lipid contents of 26.25 and 29.4% DCW were found for S. obliquus and C. sorokiniana, respectively when cultivated using wastewater. Similarly, carbohydrate contents for S. obliquus and C. sorokiniana were 18 and 17% DCW, respectively for BG11 medium. Increased in carbohydrate contents of 25% for S. obliquus, 28.4% DCW for C. sorokiniana were observed for wastewater. Microalgae tend to accumulate more lipids and/or carbohydrates under nutrient stress condition. The nitrogen and phosphorus contents in wastewater are lower than BG11 medium, which were responsible for stressed condition for microalgae. With limited nutrients in wastewater compared to BG11 medium, growth of microalgae is also lower which resulted in lower protein content. Protein content for S. obliquus and C. sorokiniana in BG11 medium were 37.83-48.8 and 25-35.3% DCW, respectively. The protein contents for S. obliquus and C. sorokiniana in wastewater medium were 16.4-27.29 and 15.8-27.3% DCW, respectively. The biochemical composition depends upon the nutrient composition of the medium and cultivation conditions. The two selected microalgae have shown potential for nutrient removal while cultivated in wastewater. The removal efficiency by S. obliquus was found to be 76.13% for COD, 98.54% for nitrogen and 97.99% for phosphate. Microalgae C. sorokiniana cultivation in wastewater removed 69.38% COD, 86.93% nitrogen and 68.24% phosphates. Increased lipid accumulation in the cells was also recorded in stressed conditions due to low nutrient availability from wastewater. After harvesting of microalgae from culture media, the water content in thick algal slurry (>85% DCW) lowers the products recovery. To overcome this challenge drying and cell disruption are required to enhance the efficiency of lipid extraction. Where drying and cell disruption increase the viability of biomass for lipid extraction process. Three biomass-drying techniques viz. sun, oven and freeze-drying and four-cell disruption techniques viz. microwave, sonication, osmotic shock and autoclave disruption were studied for their effect on recovery of major metabolites from S. obliquus. Microalgae metabolites recovery from whole cell and LEA were analysed and compared. The results showed that after lipid extraction, LEA still contained comparable protein to whole algae biomass however, the carbohydrate concentration was reduced. Oven drying exhibited the highest recovery of all the major metabolites followed by freeze-drying; sun drying however, showed lower yields. Despite lower metabolites recovery sun-drying technique is preferable at large scale due to its easy application and cost-effective nature. The main drawback of sun drying technique is weather dependence and required longer period to dry. The microwave and autoclave microalgal cell disruption improved the lipid yield but loss of other compounds was observed. In osmotic shock treatment, due to poor cell disruption efficiency low lipid were obtained and comparably lower protein loss was noticed during lipid extraction. Lipid extraction is crucial step for microalgae biodiesel production. Solvent-assisted lipid extraction is widely used technique for lipid recovery from dry or wet algae biomass. In a biorefinery approach, it is vital to choose appropriate solvents for the optimum lipid extraction whilst having minimal effect on the remaining metabolites (protein and carbohydrates) in LEA. LEA could be used for energy generation or aquaculture feed applications. Six commonly used organic solvents/ solvent systems were used for lipid extraction from wet and dry biomass. The results showed that the lipid extraction efficiency depends strongly on types of biomass as well as solvent systems selected. Lipid extraction from wet algal biomass could reduce the processing steps and save energy incurred in drying. However, the water present in wet algal slurry acts as a barrier, which results in lower lipid yield compared to the dry biomass. The results revealed that among all six-selected solvents, chloroform: ethanol (1:1 v/v) was most effective if wet biomass used specifically for lipid purpose only. To explore the biorefinery concept, isopropanol/hexane composition is the most suitable solvent system because it is less toxic and resulted in high protein (20.07% DCW) and carbohydrate (22.87%) yields in LEA. For dry algal biomass, chloroform: methanol (2:1 v/v) is an appropriate solvent system if biomass used especially for lipid (19.25%) extraction. If LEA to be used for energy and/or aquaculture feed application, DCM: methanol was found to be a suitable solvent system, which gave 32.79% protein and 26.92% carbohydrate yield. Comparatively hexane has lower lipid recovery but shown higher protein and carbohydrate yield in LEA. Due to less toxic, easy to scale up and inexpensive, hexane is preferable as a solvent for lipid extraction if LEA is to be further utilized at large scale for energy or feed application. Anaerobic digestion (AD) of organic residues is well-researched technology for biomethane production. Whole microalgae and LEA has promising potential for biomethane production. The anaerobic sludge used as inoculum for microalgal biomass digestion. Biomethane production from whole algae and products extracted algae highly depends on sludge to algae biomass ratio for higher methane production. The extraction of metabolites also changes the biochemical composition of residual biomass, which can affect the biomethane production. It is vital to understand the effect of various product-extracted algae and as well as pre-treated algae on the biochemical methane potential. In order to compare biomethane potential, four types of biomass were selected namely sun dried powder algae (SDPA), mild heat-treated algae (MHTA), LEA (using hexane as lipid extracting solvent) and protein-extracted algae (PEA). The average methane (CH4) production rate was ~ 2.5 times higher for protein and lipid ex

Sustainable production of biodiesel from microalgae by direct transesterification

Cloud points (CPs) of five vegetable oil fatty acid methyl esters (FAME) and three biodiesel mixtures estimated by a thermodynamic equation were compared to measured CPs. The results indicate that estimated CP of peanut oil FAME are similar to measured CP and for three biodiesel mixtures a minimum total saturated FAME (SFAME) concentration is required for measured CPs to be closer to estimated CPs. These comparisons provide the basis for comments on using this method for estimating CPs of 22 test data of microalgae FAME. Cold filter plugging points (CFPPs) calculated by equation CFPP = 1.0191 × CP − 2.9 with CPs verified from the thermodynamic equation was found to be identical to CFPPs reported in literature for 22 test data of microalgae FAME. Therefore these CPs were inserted in equation CFPP = CP −4.5 for another set of CFPPs. Plots of CFPPs versus percent SFAME of the 22 test data of microalgae FAME (>12 %) for these two equations indicates that CFPP is controlled by 85 % of SFAME. Calculated CFPPs of vegetable oil FAME and biodiesel mixtures using both equations for estimated and measured CPs is discussed. Low concentrations of long chain saturated FAME impacting the estimation of CPs of vegetable oil FAME is used as a rationale to discuss the role of unidentified other species (OS) in estimation of CPs of microalgae FAME.

The aim of the study was to explore the possibility of bioremediation of oil refinery wastewaters by the cyanobacterium Synechococcus sp. MK568070, isolated from the Adriatic Sea. The potential of biomass and lipid production was explored upon cultivation on oil refinery wastewater with excess CO2 after the removal of nutrients. The strain grew well in a wide range of salinities and ammonium concentrations, and was further tested on the wastewater from local oil refinery plant of various N-composition. Growth experiment under optimized conditions was used to analyze the lipid, carbohydrate and protein dynamics. The biomass yield was highly dependent on nutrient source and concentration, salinity and CO2 addition. Highest biomass yield was 767 mg/L of dry weight. Towards the end of the experiment the decline in carbohydrate to 18.9% is visible, whereas at the same point lipids, in particular saturated fatty acid methyl esters (FAME), started to accumulate within the cells. The content of lipids at the end of the experiment was 21.4%, with the unsaturation index 0.45 providing good biofuel feedstock characteristics. Fourier Transform Infrared (FTIR) spectroscopy analysis demonstrated a high degree of lipid accumulation in respect to proteins, along with the structural changes and biomass accumulation. In addition, the N-removal from the wastewater was >99% efficient. The potential of lipid accumulation, due to the functional photosynthesis even at the minimal cell quota of nutrients, is critical for the usage of excess industrial CO2 and its industrial transformation to biodiesel. These findings enable further considerations of Synechococcus sp. (MK568070) for the industrial scale biomass production and wastewater remediation.

Biodiesels are considered as promising fuels to substitute diesel fuel which can fill the gap of energy shortage while maintaining the diesel engine’s efficiency. Variations in the properties of different biodiesel fuels are caused by the varied fatty acid methyl esters (FAMEs) compositions derived from their parent oils. Therefore, correlating key properties such as cetane number (CN), kinematic viscosity (KV), iodine value (IV) and cold filter plugging point (CFPP) with FAMEs compositions of each biodiesel fuel is significant to developing whatever new types of fuels applied on diesel engines. In this study, an intelligent genetic algorithm (GA)-based back propagation neural network (BPNN) model was proposed to predict the properties of biodiesel fuels according to FAMEs compositions. The hybrid BPNN-GA model has five inputs (methyl palmitate, methyl stearate, methyl oleate, methyl linoleate and methyl linolenate) corresponding to the FAMEs compositions and outputs with estimated fuel properties, with the GA assisting on training to find out local minimum deviation and updated weighting configurations. It was found that the intelligent learning-training method proposed hybrid BPNN-GA model enabled to map the non-linear relationships between the FAMEs compositions and key properties of biodiesel fuels with fairly good agreement. The predicted value of fuel properties agrees with measured ones with R-square up to 96%, along with lower value (less than 10%) over Root Mean Square Error (RMSE) and Mean Absolute Percentage Error (MAPE) than those of other empirical correlations. In addition, a sensitivity analysis was conducted to in-depth investigate the FAMEs compositions on key properties. It was concluded that saturated FAMEs have positive impacts on CN, KV and the CFPP, while IV is typically dependent on unsaturated FAMEs. Therefore, it is attainable to formulate new types of alternative fuels based on the required properties on diesel engine applications.

Contributions of the microbial community to algal biomass and biofuel productivity in a wastewater treatment lagoon system

Lipid-accumulating microalgae are an emerging feedstock for production of liquid biofuel because of their high biomass and lipid productivity. The potential of the green microalgae, Chlorolobion sp. (BIOTECH 4031) and Chlorella sp. (BIOTECH 4026), for biodiesel production was evaluated by analyzing the effect of nitrogen starvation (0.375–1.500 g L−1 NaNO3) on growth response, oil yield, and fatty acid methyl ester (FAME) profiles of the two algal strains. Maximum biomass yields for Chlorolobion sp. and Chlorella sp. were obtained after 20 days of cultivation using the control medium (1.5 g L−1 NaNO3) with 0.873 g L−1 and 0.757 g L−1, respectively. An increasing trend in the total lipid yield was observed under a nitrogen-starved culture condition (0.375 g L−1 NaNO3). When the amount of nitrate was limited, the mean oil contents of Chlorolobion sp. and Chlorella sp. were 31.61 and 28.77% with lipid productivity of 227.84 and 151.14 mg L−1 day−1, respectively. Nitrogen starvation caused an increase in the lipid yield and a decrease in biomass production of the two microalgae. The FAME profile of the obtained algal biodiesel shows a high concentration of saturated fatty acid (SAFA) and monounsaturated fatty acid (MUFA) methyl esters which are desirable for biodiesel production. The fuel properties of biodiesel from the two microalgae were predicted based on the molecular properties of fatty acid methyl esters using empirical equations showing that the biodiesel properties of the two microalgae satisfied the set specifications of biodiesel standards EN 14214 (European) and ASTM D6751 (American). The quality properties of biodiesel obtained for Chlorolobion sp. were low density (0.89 g cm−3), low kinematic viscosity (2.79 mm2 s−1), cetane number (65.17), and oxidation stability (8.93 h). On the other hand, Chlorella sp. has low density (0.88 g cm−3), low kinematic viscosity (2.78 mm2 s−1), good cetane number (68.79), and oxidation stability (10.44 h). Hence, Chlorolobion sp. (BIOTECH 4031) and Chlorella sp. (BIOTECH 4026) have potential as raw material for production of biodiesel with superior fuel quality.