Chee Loong Teo

Enhancing growth and lipid production of marine microalgae for biodiesel production via the use of different LED wavelengths.

Wavelength of light is a crucial factor which renders microalgae as the potential biodiesel. In this study, Tetraselmis sp. and Nannochloropsis sp. as famous targets were selected. The effect of different light wavelengths on growth rate and lipid production was studied. Microalgae were cultivated for 14 days as under blue, red, red-blue LED and white fluorescent light. The growth rate of microalgae was analyzed by spectrophotometer and cell counting while oil production under improved Nile red method. Optical density result showed the microalgae exhibited better growth curve under blue wavelength. Besides, Tetraselmis sp. and Nannochloropsis sp. under blue wavelength showed the higher growth rate (1.47 and 1.64 day(-1)) and oil production (102.954 and 702.366 a.u.). Gas chromatography analysis also showed that palmitic acid and stearic acid which were compulsory components for biodiesel contribute around 49-51% of total FAME from Nannochloropsis sp. and 81-83% of total FAME from Tetraselmis sp.

Enhancing the various solvent extraction method via microwave irradiation for extraction of lipids from marine microalgae in biodiesel production.

The types of microalgae strains and the method used in lipid extraction have become crucial factors which influence the productivity of crude oil. In this paper, Nannochloropsis sp. and Tetraselmis sp. were chosen as the strains and four different methods were used to extract the lipids: Hara and Radin, Folch, Chen and Bligh and Dyer. These methods were performed by using conventional heating and microwave irradiation methods. Results revealed that highest lipid yield from the different species was obtained using different extraction methods; both under microwave irradiation. The lipid yield for Tetraselmis sp. and Nannochloropsis sp. was highest when Hara and Radin (8.19%), and Folch (8.47%) methods were used respectively under microwave irradiation. The lipids extracted were then transesterified to biodiesel and the quality of the biodiesel was analyzed using the gas chromatography.

Evaluation of direct transesterification of microalgae using microwave irradiation.

Nannochloropsis sp. wet biomass was directly transesterified under microwave (MW) irradiation in the presence of methanol and various alkali and acid catalyst. Two different types of direct transesterification (DT) were used; one step and two step transesterification. The biodiesel yield obtained from the MWDT was compared with that obtained using conventional method (lipid extraction followed by transesterification) and water bath heating DT method. Findings revealed that MWDT efficiencies were higher compared to water bath heating DT by at least 14.34% and can achieve a maximum of 43.37% with proper selection of catalysts. The use of combined catalyst (NaOH and H2SO4) increased the yield obtained by 2.3-folds (water bath heating DT) and 2.87-folds (MWDT) compared with the one step single alkaline catalyst respectively. The property of biodiesel produced by MWDT has high lubricating property, good cetane number and short carbon chain FAMEs compared with water bath heating DT.

Synergistic effect of optimizing light-emitting diode illumination quality and intensity to manipulate composition of fatty acid methyl esters from Nannochloropsis sp.

In the study, the relationship between the quality and intensity of LED illumination with FAMEs produced were investigated. Nannochloropsis sp. was cultivated for 14 days under different intensities of 100, 150 and 200 μmol photons m(-2) s(-1) of red, blue and mixed red blue LED. The findings revealed that suitable combination of LED wavelengths and intensity; (red LED: 150, blue: 100 and mixed red blue: 200 μmol photons m(-2) s(-1)) produced maximum biomass growth and lipid content. It was observed that the quality and intensity of LED significantly influenced the composition of FAMEs. FAMEs produced under blue LED has high degree of unsaturation (DU) and low cetane number while those under red LED has low DU but higher CN. The combination of red blue LED has produced FAMEs with high ignition and lubricating property and also good oxidation stability indicated by the DU and CN values which lies midway between the red and blue.

Synergistic Effects of Pulse Light Emitting Diode on Growth Rate, Lipid Content and Its Carbon Chain of Nannochloropsis Sp. in Fatty Acid Methyl Ester Production

Third generation biofuels which is biodiesel from microalgae has its share of problems such as high cultivation costs, expensive dewatering and drying process, lipid extraction and transesterification. Nannochloropsis sp. was cultivated indoor using pulse light emitting diodes LED, blue LED and red LED. Nannochloropsis sp. was cultivated for 12 d under LED pulsed at a constant frequency between 5and 100 kHz with various duty cycles (5 - 50 %) by changing the resistance compared with red and blue LED. The number of cells, lipid content and FAME composition were determined using cell counting, Nile red method and gas chromatography respectively. Results revealed that the pulse LED compared to other wavelength LED have a significant effect in the number of cell (pulse: 3.39; blue 2.83; red: 2.63 x 107 cell/mL) and exhibited a consistent lipid production stability curve compared with red and blue LED. The biodiesel produced under the pulse LED has the following characteristics: degree of unsaturation (80.41), density (881 kg/m3), viscosity (3.96 mm2/s), cetane number (61.03), iodine value (97.76), cloud point (7.1 oC), pour point (0.86 oC), CFPP (6.52 oC) and HHV (41.28 MJ.kg).