Optimization of microalgal lipid production, investigation of production and scale-up processes from laboratory to outdoor

Microalgae are photosynthetic microorganisms that have the potential to be used in the production of biodiesel which is an alternative renewable and sustainable energy source. Within the scope of this thesis, Chlorella vulgaris and Botryococcus braunii were chosen as model microalgae. In order to determine the environmental conditions which will enable maximum lipid production in both laboratory scale and outdoors, growth medium and inoculum optimization; effects of parameters including inoculation, temperature, light intensity, light – dark cycle and CO2 on panel photobioreactor cultures in laboratory scale experiments were conducted. Effects of changes in outdoor temperature and light intensity on productions were investigated and pilot scale 60 L panel photobioreactor cultures were carried out. Optimization of BG-11 growth medium resulted in modified concentrations of NaNO3, K2HPO4 and C6H8O7.xFe.yNH3 as 0.75, 0.06, 0.0075 g/L for C. vulgaris and 0.75, 0.06, 0.003 g/L for B. braunii, respectively. Optimum inoculum amount was found to be 15% for both C. vulgaris and B. braunii. Maximum biomass production in laboratory experiments was 2.72 g/L for C. vulgaris with 6% CO2 and 0.88 g/L for B. braunii with %3 CO2 in 11 day cultures. Maximum lipid production in laboratory was obtained in 11 day cultures as 424,64 mg/L for C. vulgaris with 3% CO2 and 39,30 mg/L for B. braunii with inoculation after centrifugation. Biomass and lipid productions in outdoor pilot scale panel photobioreactor cultures were 0,52 and 0,50 g/L biomass; 18,21 and 28,18 mg/L lipid for C. vulgaris and B. braunii in 13 and 14 day cultures, respectively. In terms of biomass and lipid production as well as fatty acid composition, the best choice for the production of biodiesel is found to be C. vulgaris supplied with 3% CO2.