Effect of inorganic micronutrients on cell growth, photosynthetic pigments and biochemical compositions of Arthrospira (Spirulina) maxima

Abstract

Underground seawater from Jeju Island, Korea (so called Jeju magma seawater, JMS) has high amounts of inorganic micronutrients as much as 7.5 to 55 times compared with the concentrations of zinc (Z, 0.019 mg/L), iron (F, 0.015 mg/L), manganese (M, 0.008 mg/L), vanadium (V, 0.015 mg/L), selenium (S, 0.013 mg/L) and germanium (G, 0.002 mg/L) in natural seawater. The micronutrients are essential minerals for cell growth and photosynthetic metabolism of marine algae. In recent year, mineral rich water has been applied to many fields such as food, beverage and bio-industry based on functionality, and more recently to marine bio-industry. However there is no scientific information about the relation between the inorganic micronutrients of JMS. The purpose of this study was to investigate the inorganic micronutrients combination effect of JMS on cell growth and biochemical compositions of cyanobacterium, Spirulina maxima. Screening experiment for discovering of beneficial combinations to cell growth was conducted in 10 mL-flasks for 14 days. Optical density (OD) of 64 modified culture media containing cells was measured by spectrophotometric measurement (λ=664 nm) which are made by mixed 6 mineral reagents under different concentration regimes referred by JMS concentration. After then, selected 8 combinations of the micronutrients were used for 20 L-scale cultivation to compare the biochemical differences and growth performance in scale-up culture. In 20 L-scale cultivation, the final biomass and specific growth rate of S. maxima in the culture media with single Z and mixed M+Z combinations were significantly higher than others. Protein levels of cells in mixed M+Z combination (568.61±5.85 mg/g) were significantly higher than the level of control (525.30±5.20 mg/g). Photosynthetic pigments of chlorophyll-a and C-phycocyanin of cells were also significantly increased in the media contains single Z (5.75±0.18 mg/g) and mixed M+Z+V (101.91±mg/g) combinations than control, respectively (p<0.05). These results indicated that the M and Z of JMS have significant effects on cell growth and biochemical compositions of S. maxima.