Indian Journal of Experimental Biology Vol. 51, March 2013, pp. 262-268 Biodiesel production from marine cyanobacteria cultured in plate and tubular photobioreactors B Karpanai Selvan, M Revathi, P Sobana Piriya, P Thirumalai Vasan, D Immuanual Gilwax Prabhu & S John Vennison* Department of Biotechnology, Anna University-BIT Campus, Tiruchirappalli 620 024, India Received 28 October 2011; revised 12 November 2012 Carbon (neutral) based renewable liquid biofuels are alternative to petroleum derived transport fuels that contribute to global warming and are of a limited availability. Microalgae based biofuels are considered as promising source of energy. Lyngbya sp. and Synechococcus sp. were studied for the possibility of biodiesel production in different media such as ASNIII, sea water enrichment medium and BG11. The sea water enrichment medium was found superior in enhancing the growth rate of these microalgae. Nitrogen depletion has less effect in total chlorophyll a content, at the same time the lipid content was increased in both Lyngbya sp. and Synechococcus sp. by 1.4 and 1.2 % respectively. Increase in salinity from 0.5-1.0 M also showed an increase in the lipid content to 2.0 and 0.8 % in these strains; but a salinity of 1.5 M has a total inhibitory effect in the growth. The total biomass yield was comparatively higher in tubular LED photobioreactor than the fluorescent flat plated photobioreactor. Lipid extraction was obtained maximum at 60 ºC in 1:10 sample: solvent ratio. GC-MS analysis of biodiesel showed high content of polyunsaturated fatty acids (PUFA; 4.86 %) than saturated fatty acid (SFA; 4.10 %). Biodiesel production was found maximum in Synechococcus sp. than Lyngbya sp. The viscosity of the biodiesel was closely related to conventional diesel. The results strongly suggest that marine microalgae could be used as a renewable energy source for biodiesel production. Keywords: Biodiesel, LED photobioreactor, Lipid, Lyngbya sp., Salinity, Synechococcus sp. The effective use of fossil energy resources in an economic way still remains as a major challenge. The main drawback of fossil fuel is that it is a finite non- renewable resource and will be depleted in the near future or one day be exhausted. Since the last few decades, fossil fuels have become an integral part of day to day human lives. Specifically, these fuels are burned to produce energy for transportation and electricity generation, as these two sectors have played a vital role in improving human living standard and accelerating advance technological development. Biodiesel is a transportation fuel that has gained popularity over the past decade. With the dwindling reserves of fossil fuels, it is now more important than ever to search for transportation fuels that can serve as alternatives to crude oil-based fuels such as gasoline and diesel. Biodiesel decomposes well and reduces toxic exhaustion gases and dust hence is environmental friendly and has a high flash point and is easy to handle or store 1 . Among primary feedstocks for biodiesel, microalgae are currently considered to be one of the most promising alternative resources. Microalgae are microscopic photosynthetic organisms that are found in both marine and fresh water environments. Microalgae have attracted attention for bioenergy production because they can produce oil in the cell body 2 . Unlike oil crops, microalgae grow rapidly and many are exceedingly rich in oil. Although the growth of the microalgae varies depending on the characteristics of the species, they mostly double their biomass within 24 h 3 . Biomass doubling time during exponential growth is commonly as short as 3.5 h. Oil content in microalgae ranges from 20-50% and it can exceed 80% by weight of dry biomass 4 . Microalgae with high oil productivities are desirable for biodiesel production. Interestingly biomass production in microalgae may be combined with direct bio-fixation of waste CO 2 to the value of 1.8 kg per kg of dry algal biomass. They are, therefore considered as promising candidates for the industrial level production of biodiesel. The composition and fatty acid profile of lipids extracted from a particular species is further affected ____________ *Correspondent author Telephone: +91 – 9486230714 E-mail: johnvennison36@gmail.com