Biodiesel production from Dunaliella salina

International Journal of Renewable Energy Research, 2014

Cyanobacteria and microalgae can be suitable microorganisms for the production of biofuels to meet our needs of safe and clean sources of energy. Among them, Dunaliella strains are considered good feedstocks for biofuel production. In this regards, a naturally isolated strain of Dunaliella salina was investigated to be used as potential biodiesel feedstock. The microalgal strain was isolated from water samples collected from Maharlu Salt Lake, 30 km southeast of Shiraz, Iran. At the end of exponential phase of growth, total content of the lipids was extracted, esterified and then identified using GC/MS analysis. Several types of fatty acid methyl esters (FAMEs) were identified in the isolated microalgae. The composition of fatty acids in the studied species of microalgae was mainly hexadecanoic acid methyl ester and tetradecanoic acid methyl ester.

Botswana International University of Science and Technology (BIUST), 2020

Production of biodiesel from microalgae has received worldwide recognition as an alternative to petroleum diesel. The process involves culturing, harvesting, drying, extraction, transesterification and characterisation of the microalgae biomass to biodiesel. The research aimed to investigate the potential of Dunaliella salina microalgae in Botash Company’s solar ponds for biodiesel production. Optimum salinity and nutrients concentrations that produced maximum biomass and lipids were investigated. Furthermore, the lipids and the biodiesel produced were identified, quantified and characterised. D. salina microalgae were isolated from the solar ponds and cultured in f/2 media under optimum conditions. One Factor at A Time (OFAT) design was used to determine the optimum salinity for the growth and lipid accumulation of the microalgae. A salinity concentration of 2.5 M produced the highest biomass concentration of 2480 mg L-1, biomass productivity of 58.40 mgL-1d-1, lipid content of 22.65 % and lipid productivity of 14.43 mgL-1d-1. In regard to nutrient optimisation, Plackett-Burman and Box-Behnken designs of response surface methodology (RSM) were used to optimise the culture media by selecting significant nutrients and their concentrations for culturing D. salina and promotion of lipids accumulation. In the first stage, Plackett-Burman method identified NaHCO3, NaH2PO4.2H2O and NaNO3 as factors that significantly influenced the biomass concentration, lipid content and lipid production. MgSO4.7H2O and micronutrients solution had a significance effect on the lipid content. The relationship on biomass concentration, lipid content and lipid production were predicted using a model that had an R2 value of 99.3% with a P-value of 0.000. In the second stage using Box-Behnken design, the nutrients selected in the first stage were further optimised and a predicted model was generated with an R2 value of 95.8%. The optimum medium that constituted 1302.4 mgL-1 NaHCO3, 22.5 mgL-1 NaH2PO4.2H2O, 181.1 mgL-1 NaNO3, 44.7 mgL-1 CaCl2, 2355.0 mgL-1 MgSO4.7H2O, 5.6 mlL-1 of micronutrients solution produced maximum lipid production of 181.1 mgL-1, which is 12.3% more than the 127.0 mgL-1 produced using the un-optimised medium. After approximately 36 days of culturing the cells were harvested and used to extract lipids by solvent extraction method, Thin Layer Chromatography (TLC) screened and approximated lipids to linoleic acid, oleic acid, and some triglycerides. Biodiesel was produced from the extracted lipids using alkali transesterification process. Fourier Transform Infrared (FTIR) identified chemical bonds in biodiesel with a strong peak at 1743 - 1742 cm-1 wavelength as triglycerides ester carbonyl functional group. Furthermore, the D. salina biodiesel’s chemical composition was quantified using Gas Chromatography (GC) and Mass Spectrometry (MS) spectrum that verified the presence of monounsaturated methyl esters. The physiochemical characterisation of D. salina biodiesel was in the recommended specification of the EN 14214, ASTM D6751 and SANS 1935:2004 standards indicating a good quality of the fuel. The D. salina biodiesel when compared to sunflower biodiesel and petroleum diesel had the highest ignition temperature, burnout temperature, ignition index and also the least comprehensive performance reflecting good thermal properties of the fuel. The thermal kinetics of D. salina biodiesel show a high pre-exponential factor (A) and Gibbs energy (∆G) but low activation energy (E) and entropy (∆S). The enthalpy (∆H) and higher heating value (HHV) were comparable to the ones for sunflower biodiesel and petroleum diesel. Based on the results of physio-chemical and thermal characterisation, the D. salina biodiesel could be used in boilers such as the ones in Botash Company for ignition and steam production purposes. In conclusion, the study was able to enhance lipids production during culturing stage, produce biodiesel through an effective selection of the best catalyst during the transesterification stage, identified and characterise the biodiesel.

Russian Journal of Marine Biology, 2019

Dunaliella salina is a unicellular microalga with the potential of industrial applications. Commercial-scale cultivation of D. salina requires extensive efforts on cost reduction. This can be achieved by minimization of nutrient cost and maximization of specific growth rate and productivity. To this end, in this study, mixotrophic cultivation of D. salina on crude glycerol (by-product of calcinated-fatty acid (CaFA) production process) was investigated in shake flasks and the influences on protein, carotenoid and chlorophyll contents of the cells were studied. The highest maximum specific growth rate and biomass productivity was achieved by cultivation on 2.5 g/L crude glycerol. The protein content was more than two folds and the carotenoid content was more than 60% higher than that of autotrophic cultivation. Subsequently, continuous cultivation of D. salina on crude glycerol in a helical photobioreactor was performed at the dilution rate of 0.52/d. The biomass productivity of 2.3 × 10 6 cell/(mL d) was achieved which was more than 75% of the values for previously reported autotrophic cultivations. Conclusively, continuous cultivation of D. salina on by-product of CaFA production process could be a potential process technology for production of D. Salina.

Fuel, 2020

Due to expensive culture realizations and low lipid yields, microalgae-based biodiesel production still lacks economic viability at an industrial-scale. Optimization of lipids and fatty acid methyl esters (FAMEs) distribution is a necessary condition to get sustainable microalgae biodiesel production. Nutritional sources (nitrogen, phosphorous, carbon and iron) influence the lipid accumulation and biomass production yield. The aim of this study is to get high-quality biodiesel by a microalgae-yeast co-culture based on the selection of culture media micronutrients' distribution. A response surface-based combination of NaNO 3 , K 2 HPO 4 and FeSO 4 *7H 2 O nutrients increases biomass and lipids accumulations. The obtained highest biomass and lipids contents are 1.68 gL −1 and 27.77%, respectively. Under the selected optimized micronutrients' composition, high-saturated fatty acids are obtained if high ratio of N/P (6:1 and 11:1) and unsaturated fatty acid under N/P ratio of (9:1) are considered. These results suggest microalgae-yeast co-culturing under controlled N/P ratio in the culture medium produce desirable lipids distributions, yielding better biodiesel quality and equilibrium between biomass and lipids accumulation. The selected micronutrient combination (with the selected N/P ratio) leads to augment the lipids content which is transformed into biodiesel. Biodiesel quality (determined by cetane number, iodine value, cloud point, oxidation stability, viscosity), is evaluated considering microalgae lipids and FAMEs produced by transesterification process. Fourier transform infrared (FTIR) corroborates the lipids distribution, which can be used to produce high quality biodiesel. Gas chromatography (GC) verifies the production of desirable methyl esters (C16 and C18).

Zeitschrift fur Naturforschung. Section C, Biosciences

Nannochloropsis salina was cultured batch-wise to evaluate the potential of the alga to produce biodiesel. The cells were harvested at the end of the exponential growth phase when the concentration was 18 x 10(6) cells/mL culture. The growth estimated as dry weight from this cell number was (3.8 +/- 0.7) mg/L. The lipid and triglyceride contents were 40% and 12% on a dry weight basis, respectively. The amount of the ratio triglycerides/total lipids was approximately 0.3. The composition of triglyceride fatty acid methyl esters (biodiesel) was analysed by gas-liquid chromatography and identified as: C14:0, C16:0, C16:1, C18:0, C18:1, C18:2, C18:3, C20:1, and C20:5. The ratio of unsaturated to saturated fatty acid contents was approximately 4.4. Additionally, the characterization of each individual fatty acid ester was discussed with regard to the fuel properties of biodiesel produced by the alga.

Grasas y Aceites, 2010

BioEnergy Research, 2012

The viability of algae-based biodiesel industry depends on the selection of adequate strains in regard to profitable yields and oil quality. This work aimed to bioprospecting and screening 12 microalgae strains by applying, as selective criteria, the volumetric lipid productivity and the fatty acid profiles, used for estimating the biodiesel fuel properties. Volumetric lipid productivity varied among strains from 22.61 to 204.91 mg l −1 day −1 . The highest lipid yields were observed for Chlorella (204.91 mg l −1 day 1 ) and Botryococcus strains (112.43 and 98.00 mg l −1 day −1 for Botryococcus braunii and Botryococcus terribilis, respectively). Cluster and principal components analysis analysis applied to fatty acid methyl esters (FAME) profiles discriminated three different microalgae groups according to their potential for biodiesel production. Kirchneriella lunaris, Ankistrodesmus fusiformis, Chlamydocapsa bacillus, and Ankistrodesmus falcatus showed the highest levels of polyunsaturated FAME, which incurs in the production of biodiesels with the lowest (42.47-50.52) cetane number (CN), the highest (101.33-136.97) iodine values (IV), and the lowest oxidation stability. The higher levels of saturated FAME in the oils of Chlamydomonas sp. and Scenedesmus obliquus indicated them as source of biodiesel with higher oxidation stability, higher ). The third group, except for the Trebouxyophyceae strains that appeared in isolation, are composed by microalgae that generate biodiesel of intermediate values for CN, IV, and oxidation stability, related to their levels of saturated and monosaturated lipids. Thus, in this research, FAME profiling suggested that the best approach for generating a microalgae-biodiesel of top quality is by mixing the oils of distinct cell cultures.

The viability of algae-based biodiesel industry depends on the selection of adequate strains in regard to profitable yields and oil quality. This work aimed to bioprospecting and screening 12 microalgae strains by applying, as selective criteria, the volumetric lipid productivity and the fatty acid profiles, used for estimating the biodiesel fuel properties. Volumetric lipid productivity varied among strains from 22.61 to 204.91 mg l −1 day −1 . The highest lipid yields were observed for Chlorella (204.91 mg l −1 day 1 ) and Botryococcus strains (112.43 and 98.00 mg l −1 day −1 for Botryococcus braunii and Botryococcus terribilis, respectively). Cluster and principal components analysis analysis applied to fatty acid methyl esters (FAME) profiles discriminated three different microalgae groups according to their potential for biodiesel production. Kirchneriella lunaris, Ankistrodesmus fusiformis, Chlamydocapsa bacillus, and Ankistrodesmus falcatus showed the highest levels of polyunsaturated FAME, which incurs in the production of biodiesels with the lowest (42.47-50.52) cetane number (CN), the highest (101.33-136.97) iodine values (IV), and the lowest oxidation stability. The higher levels of saturated FAME in the oils of Chlamydomonas sp. and Scenedesmus obliquus indicated them as source of biodiesel with higher oxidation stability, higher ). The third group, except for the Trebouxyophyceae strains that appeared in isolation, are composed by microalgae that generate biodiesel of intermediate values for CN, IV, and oxidation stability, related to their levels of saturated and monosaturated lipids. Thus, in this research, FAME profiling suggested that the best approach for generating a microalgae-biodiesel of top quality is by mixing the oils of distinct cell cultures.

International Journal of Current Microbiology and Applied Sciences, 2019

Delta Journal of Science, 2016

The aim of this study was to investigate the growth, lipid content and lipid productivity of the biodiesel promising microalgae Scenedesmus obliquus and Micractinium reisseri grown in batch culture using four different freshwater growth media, namely Chu-10, KC, Flory and Kuhl's medium to identify the most suitable medium for high lipid production for each species. The Results confirmed that Kuhl and KC showed the highest biomass productivity for S. obliquus and M. reisseri (0.05 and 0.07g L -1 d -1 , respectively). The Lipid content and lipid productivity were estimated at four different growth phases (early, middle, late exponential and stationary phase).The results revealed that, M. reisseri showed the highest lipid productivity at stationary phase (17.08 mg L -1 d -1 ), while S. obliquus showed lipid productivity of 12.61 mg L -1 d -1 which was insignificant with that at the late exponential phase (12.55 mg L -1 d -1 ). The fatty acids profile of S. obliquus and M. reisseri at stationary growth phase showed that both of them were suitable as feedstock for biodiesel production because of their high saturated fatty acids content that represented by 81.34% and 72.51% of the total fatty content, respectively. Palmitic acid (C16:0) was represented by 15.74 and 16.06 % in the two studied species, respectively that increase the biodiesel quality for each strain. This study suggests M. reisseri cultivated on KC medium to provide high lipid productivity which offers a promise to be one of the sources of biodiesel.