Effects of alternate nutrient medium on microalgae biomass and lipid production as a bioenergy source for fuel production

Abstract

Over last three decades, worldwide researchers are researching on biomass feedstock, as it is a promising renewable and zero-carbon source of energy. Fuels produced from biomass are called as biofuels; biofuels can play an important role in meeting the energy demand and can help to reduce global warming. As compared to other biomass feed stocks (terrestrial plants) microalgae is considered as a promising source due to its high potential to produce lipids by absorbing nutrients from the wastewater, without affecting the usage of arable land and fresh water resources. Among the different microalgae strains, green microalgae have higher growth rate with more lipid content. Biomass production and lipid accumulation of microalgae are limited by various factors, such as CO2 supply, temperature, aeration, salinity and concentration of nutrients in the medium. Nutrient concentration and its limitation is one of the effective limiting factor to increase the lipid accumulation in microalgae.During the present study, three various alternate nutrient concentration experiments viz. higher strength, full strength and half strength, and one standard Bold’s Basal Medium (BBM) with full strength have been prepared to investigate the effects of alternate nutrient medium and different nutrient concentrations on biomass and oil productivity of green microalgae Chlorella Sorokiniana-5673. The cultivation was carried in a semi-controlled open pond environment and all experiments were conducted in duplicate. The alternate nutrient medium was prepared by using agriculture fertilizers, as source of major nutrients and tap water as a substrate. The growth performance of microalgae was observed by UV–visible spectrophotometer and the oil extraction was carried by Bligh–Dyer Method. The growth performance, biomass productivity and oil productivity of all experiments were observed. These findings indicate that alternate nutrient medium gives better performance than the standard BBM and low nutrients concentration medium showed high oil productivity. Thus the open pond cultivation of microalgae with alternate nutrient medium viz. agriculture fertilizer medium is an efficient cultivation method to produce more biomass and oil.