Effect of Potassium Nitrate on Biomass and Lipid Yield of Nannochloropsis sp. for Biofuel Production

Abstract

Energy crisis is an unavoidable problem in current world. Fossil based energy pose a serious conflict on energy demand due to its rapid depletion as well as Green House Gas emissions to the atmosphere with its combustion. Biodiesel as a renewable energy is a where microalgae are studied as an oil source. Nannochloropsis sp. has been identified to contain a higher oil yield and more suited for outdoor cultivations. Many aspects that effect on growth and oil productivity of Nannochloropsis sp. such as light, pH, temperature, and salinity have been studied previously. Potassium nitrate has been identified to be increasing the oil content in Nannochloropsis sp. Previous studies revealed that there is a significant relationship with potassium nitrate and oil yield of Nannochloropsis sp. Therefore, effect of potassium nitrate levels on the productivity of biomass content and lipid content of Nannochloropsis sp was studied in the present study to understand optimum levels. Micro algal cell growth rate was examined by Spectrophotometer using 665 nm wave length. Different potassium nitrate concentrations from 0.0035-0.0075 mol/L were used with Guillard and Ryther’s F growth media. The highest oil yield of 3.5% was observed in 0.0055 mol/L potassium nitrate concentration but there is no significant difference among the treatments. The highest biomass yield was observed as 1.7 g/L in potassium nitrate concentration 0.0045 mol/L. Higher cell growth was achieved at KNO3 concentration of 0.0055 g/L. Guillard and Ryther’s F growth media can be improved by adding potassium nitrate to achieve higher biomass and lipid productivity.
Keywords: Nannochloropsis sp., Oil yield, Biomass, Pottasium nitrate