The use of algae as an alternative source of bioenergy (e.g., for making biogas or bioethanol) has a large potential. Viewing algae as a photosynthetic unit for production of biomass, it could potentially provide billions of tons of biomass without compromising food supply or agricultural land. Microalgae are microscopic plants that are primary synthesizers of organic matter in aquatic in aquatic environment. They have high surface to volume ratio enabling the rapid uptake of nutrients and CO 2, and, have a faster cell growth rate than land based plants. But algae biomass for energy is still in its infancy. Key issues affecting large scale algae based production of bioenergy are: selection of species, nutrient requirements, cultivation and harvesting techniques and conversion technology. This research investigated the cultivation and harvesting of unique hypersaline, nitrogen-fixing, exopolysaccharide producing cyanobacteria Synechococcus sp 0011 and methods to increase the exopolysaccharide production by light exposure and intensity, and, CO 2 concentration. We obtained an average maximum specific growth rate of days -1 using air and a 13/11 hour light/dark cycle. Observations showed that polysaccharide production increased when using high concentrations of CO 2 in headspace and 24 hours light exposure during stationary growth phase. ABSTRACT BACKGROUND Four runs each in triplicate were carried out. A bank of two 20 W fluorescent lights kept on a 13/11 on/off cycle were used to give light and heat to the chamber. Air was sparged at 0.5 L/min The temperature was kept constant at 30 °C. Batch and semi-continuous batch were used to determine the maximum growth rate under the described conditions. During Batch phase there was no addition of media to the reactors while Semi-continuous phase required dilution of culture broth with media and water, accounting for evaporative loss, once sampling was done. METHODS RESULTS Synechococcus sp 0011 is a photoautotrophic, nitrogen fixing, hypersaline, polysaccharide secreting natural cyanobacteria (blue-green algae) strain isolated from the Florida Keys. The exopolysaccharide produced by this polymer-producing strain of unicellular cyanobacteria, Synechococcus BG011, could be used as a possible feedstock for biofuel production. PHLIPS ET AL., 1989 D10 The observed maximum specific growth rate on averaging over the 4 runs was days -1 while the maximum specific growth rates for the separate runs were between days -1. The optical density in each run went up to a maximum of 1.3 and an average optical density over the triplicates was observed to be 0.66 ± after 15 days with a maximum corresponding cell density of 0.5 g/L To grow BG011 a isothermal (30 °C) growth chamber was designed. The heat and the light needed was provided by a bank of cool white fluorescent lamps. Aeration was used for cell synthesis and agitation. Appropriate media that mimic the ocean conditions was used. Optical density was used to measure biomass concentration. This is an ongoing experiment and we are currently in Stage 1 which deals with maximizing growth and exopolysaccharide production. Sampling was carried out at 24 hour intervals with sampling size maintained at 1.5 ml during the batch phase and 5 ml during the semi- continuous phase. The sample optical density was determined using a Milton Roy Spectronic 401 Spectrometer using λ=540 nm. Dry weight analysis was carried out on samples from Run 4 where the samples were centrifuged and washed at least 6 times to bring the salinity to zero before determining dry weight CONCLUSIONS Growth Kinetics of Synechococcus sp. was studied and replicated Maximum specific growth rate of days -1 was observed on average with aeration Dry cell weight was verified to showed a linear relationship with optical density Maximum cell density obtained was 0.5 g/L Exponential growth phase was observed to cease at around 15 days of growth FUTURE WORK Enrichment of air supplied to the photobioreactors with CO 2 at different concentrations to test effect on growth Characterization of exopolysaccharide Optimize production of exopolysaccharide with respect to salinity, partial pressure of CO2, light intensity and exposure time, pH and micronutrients. Adapt, optimize and validate techniques commercially developed for saccharification of polysaccharides and ligno-cellulosic biomass for saccharification of exopolysaccharide. Anaerobically digest exopolysaccharide containing cell cultures to quantify methane potential and identify best temperature range for digester operation. REFERENCES Growth, photosynthesis, nitrogen fixation and carbohydrate production by a unicellular cyanobacterium, Synechococcus sp. (Cyanophyta). Edward J Phlips, Carolyn Zemman & Phyllis Hansen. Journal of Applied Phycology, 1 (1989) 137 – 145 DEVELOPMENT OF AN INTEGRATED ALGAL BIOREFINERY FOR POLYSACCHARIDE AND BIOFUEL PRODUCTION CESAR M. MOREIRA, 1 YATIN BEHL, 2 RAGHAVENDRAN MURALI, 2 BRIAN WOLFSON, 2 SPYROS SVORONOS, 2 EDWARD PHLIPS, 3 PRATAP PULLAMMANAPPALLIL 1: DEPARTMENT OF AGRICULTURAL AND BIOLOGICAL ENGINEERING,2: DEPARTMENT OF CHEMICAL ENGINEERING,3: SCHOOL OF FOREST RESOURCES AND CONSERVATION,UNIVERSITY OF FLORIDA, GAINESVILLE FL, USA OD VS TIME GROWTH RATE DRY CELL WEIGHT (g/L) AVERAGE OPTICAL DENSITY