EXTRACTION AND QUANTIFICATION OF INTRACELLULAR LIPID AS POTENTIAL BIOFUEL FROM ALGAL BIOMASS
Authors: M. I Auyo, , S. Abdullahi , A. Ahmed 
Published: March 2023

Purpose: Fossil fuels occuring as ancient algae deposit is the major source of energy that we energise our engines today. It is a limited non-renewable resource that will eventually run out. Algae have been reported to generate renewable fuels known as biofuel. It is in this regards that this work was carried out to determine, extract and quantify intracellular lipid in algal biomass for subsequent use as biofuel.

Methodology: Four average sized ponds within Federal University Dutse Campus, Nigeria (11.00̊ N to 13.00̊ N and longitude 8.00̊ E to 10.15̊ E and altitude 465.5m). were randomly selected and 20ml pond water were collected from top, middle and bottom of each pond. 60ml pond water was taken to laboratory and were processed by first preparing the media.  3ml NPK gel fertilizer was mixed with distilled water and autoclave at 121°C for 15 min. Bold's Basal Medium (BBM) consisting stock solution and BBM consisting of trace elements were separately mixed with distilled water. 10 ml of the stock solution and 1.0 ml of the trace elements were autoclave at 121°C for 15 min. The media (BBM and fertilizer) were cooled at room temperature, antibiotics (penicillin G, di-hydro-streptomycin sulfate and gentamycin sulfate) were added and pH adjusted to 7.5 and the media were kept ready for used. Isolations of species were carried out by serial dilution using BBM and under microscope sterile syringe and needles were used to isolate some target cells from the samples. Thus, four different algal species; Euglena, Spirogyra, Selenastrum and Chlorella were isolated and identified.  Culturing of the microalgae isolates was carried out by transferring into 50 ml growth chamber containing BBM and NPK fertilizer media separately and cultured using sunlight for 10 days under controlled pH.  Two successfully grown species; Spirogyra and Selenastrum were transferred aseptically into four constructed photobioreactors containing 400 ml liquid media; two containing BBM and the other fertilizer media. Nile Red was used to stain the algal wet biomass and observed under microscope and subsequently photographed. Microalgal cultures were dewatered by repeated centrifugations at 4000 rpm and the supernatants were discarded and the micoralgal biomass rinsed with deionised water to remove the residual salt and later dried using thermostatic drying oven and subsequently grinded. Growths were determined through dry weight determination and growth percentage was obtained as:  dried biomass of a species from each medium/total dried biomass of the species x 100. The dried algal biomass was extracted and evaporated and extracts were heated using vacuum rotary evaporator to separate the solvent (chlorofoam) from the extracts. Transesterification was carried out and first prepared solution was poured into a conical flask containing 5.2 g lipid of Selenastrum species and the second solution was poured into a conical flask containing 2 g lipid of Spirogyra spp. Both flasks were heated over constant temperature magnetic stirrer with condenser attached maintained at 60°C.m Phase separation was carried out along with purification in which soap and other impurities were removed and resulting solution remained flammable biodiesel.

Findings: While Euglena and Chlorella failed to grow in the initial media, both Spirogyra, and Selenastrum produced significant amount of biodiesel with Selenastrum species producing higher quantity than that obtained from Spirogyra, hence a potential source of the fuel.