P. tricornutum was cultured in a panel PBR system, with different light path (1, 3, 5, 7 and 10 cm), 50% nitrogen reduction and with 20% inoculation densities. Lipid, protein and biomass rate were determined. The highest lipid content (34.6%) for P. tricornutum in the study was obtained from the culture with 1.064gl(-1) biomass rate, 8.50% protein it the panel PBR system with 50% nitrogen reduction and 7 cm light path. The lowest lipid content and highest protein were found as 29.76%, 10.12% respectively, at 1 cm light path PBR system with 50% nitrogen reduction. The highest OD and lowest chl a were found in the 7 cm light path PBR system with a 50% nitrogen reduction.