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

Abstract

Underground seawater sampled at 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 required for growth and photosynthetic metabolism of marine algae. However there is no information about the relation between the inorganic micronutrients of JMS and marine algae, few studies of land plant cultivation have been reported. The purpose of this study was to investigate the combination effect of inorganic micronutrients of JMS on cell growth and biochemical compositions of cyanobacterium, Spirulina maxima. Screening experiment of 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 eight combinations of the micronutrients were used for 20 L-scale cultivation to compare the biochemical differences and growth performance in scale-up culture. In 10 mL-scale cultivation for screening, the highest OD value was recorded in the medium containing mixed combination of M and V (M+V), followed M+Z+V and M+Z+F combinations. In scale-up 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 were significantly high in mixed M+Z combination (p<0.05). Photosynthetic pigments of chlorophyll-a and C-phycocyanin of cells were also significantly increased in the media of single Z and mixed M+Z+V combinations, 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.