Evaluating Indigenous Microalgae as Potential Source for Bioethanol production

Abstract

Increasing energy demand and consumption leading to early fossil fuels depletion and severe energy crises along with environmental hazards. Biofuels could be the only possible sustainable alternative energy approach. Microalgae being third generation feedstock seems to be an attractive source for biofuels production as it can accumulate high amount of lipids and carbohydrates content in its biomass. The current study was primarily focused on evaluation of indigenous microalgae for bioethanol and biodiesel production. 5 microalgal strains were isolated from local fresh water samples and MSB strain with highest growth rate, biomass productivity, total carbohydrates and sugars content of 0.175~/day, O.l87gL-1 day-I, 2.23% and 3.14% respectively, was selected for further its optimization and bioethanol production. Effect of four different parameters was observed on MSB strain, and highest growth rate and biomass productivity was achieved at pH 7 when urea used as nitrogen source with proper aeration and 24 h continuous light supply. Highest biomass production of 1.75g1L was noticed on average temperature of 29°C in the month of August. In optimized conditions strain was observed with increase in total carbohydrates, sugars and lipids content up to 8% ,7.5% and 19.6% respectively and after 11 days nitrogen starvation these concentrations further increased up to 10%, 9% and 22.1 % accordingly. Dried biomass was pre-treated with dilute acid hydrolysis and maximum sugars extraction was achieved when treated 5g1L biomass with 1% concentrated Sulfuric acid. Bioethanol was produced from extracted sugars hydrolysate in 72 h yeast based fermentation and its production was indicated by yeast culture growth along with gas collection in sample reactor. GC-MS was performed for bioethanol yield and quality evaluation (results are awaiting). FTIR analysis was performed for biodiesel production confirmation and C=O of ester stretch was observed at 1734.20 and 1740.93 in microalgae oil while this stretch was located at 1742.14 in biodiesel. C-O of ester stretch in microalgal oil spectra was observed at 1160.90 while it was existed at 1107.96, 1157.20, 1193.71 in biodiesel spectra and presence of these ester groups indicated the biodiesel production from algal oil. With respect to this study it can be concluded that indigenous microalgae can be effectively optimized for enhanced biofuels production.