Anju Arya, Rashmi Tyagi and Durlubh Kumar Sharma
Application of Nitrogen and Phosphorus Stress Conditions for Biomass and Oil Production by Chlorella vulgaris
Biodiesel from higher plantshas a number of limitations like burden on limited agricultural land and fresh water resources, especially in poor developing nations. On the other hand wastelands can be effectively used for the cultivation of microalgae and potential yields from many green algae have been reported to be many folds to that obtained from the oil crops. Productivity in natural habitats is generally limited by low nitrogen and phosphorus content. Present study deals with the application of main nutrients nitrogen and phosphorus stress conditions commonly found in natural water bodies on stimulating the biofuel components oils in Chlorella vulgaris, a unicellular freshwater green alga and a potential feedstock for biodiesel. Oils from the algal biomass were extracted in chloroform-methanol (2:1) and identified by GC-MS. Significantly reduced concentrations of the nutrients Ca(NO3 )2 and K2 HPO4 from the control values of Chu-10 medium positively affected the oil content without much affecting the growth. There was also a significant effect on the relative ratios of various types of oils produced by the algal strain in response to the nutrient stress conditions. Mostly C14 to C26 fatty acids were identified, with palmitic, oleic and stearic acids being the major ones. The relative proportion of the desirable biofuel component, palmitic acid, was increased significantly under NO3 - and PO4 3- stress conditions. These findings suggest that monitoring the concentrations of a few nutrients may lead to significant enhancement in quantity as well as the desirable biofuel components with substantial growth for commercial cultivation of C. vulgaris for bioenergy production.
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