Evaluation of Media and Nitrogen:Phosphorous Ratios for Optimal Growth of Biotechnologically Important Unicellular Microalgae

Abstract

This study was conducted to assess the impact of varying nitrogen:phosphorous ratios of liquid culture media on biomass productivity in microalgal strains of biotechnological importance. Four strains of microalgae were grown in standing cultures at 28°C for up to 14 days with a light:dark photoperiod of 15 h:9 h. A commercially available freshwater algal growth medium (AG), modified blue-green 11 (mBG11), modified Bold (mBold), and modified Chu#13 (mChu) were used as the liquid media. Algal species Botryococcus braunii (UTEX 572) cultured in AG, Neochloris oleoabundans (UTEX 1185) cultured in mChu, and Scenedesmus obliquus (UTEX 1450) cultured in mChu attained the shortest doubling times of 5.2, 3.3, and 3.6 days, respectively for each media/algae combination. Doubling times for Scenedesmus obliquus (UTEX 393) in AG and mChu media were similar, 3.5 +/0.1 and 3.6 +/0.1 days, respectively. An N:P mass ratio of 5.5:1 (mChu) and 30.5:1 (AG) promoted the most rapid biomass production, while the two media with ratios of 2.5:1 (mBold) and 47.6:1 (mBG11) had lower biomass productivities. Macronutrients were above minimum concentrations required for growth in each media; therefore, N:P ratio is an important consideration, and media with N:P ratios within the range of 5.5:1 to 30.5:1 are the most desirable for green algae biomass production.