Cell growth and biochemical variations of Arthrospira (Spirulina) maxima under different regimes of inorganic micronutrients

Abstract

Underground seawater of Jeju Island, Korea (named as Jeju magma seawater, JMS) has large amount of inorganic micronutrients as much as 7.5 to 55 times compared with natural seawater, which are 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). The 6 micronutrients are the essential elements for the photosynthetic metabolism and growth of marine algae. However, there is no information about the effect of inorganic micronutrients in JMS to marine algae, few studies of plant cultivations have been conducted. The purpose of this study was to investigate the effects of micronutrients on growth of blue-green alga, Spirulina maxima in the modified conventional medium using different concentration regimes of inorganic components same as JMS. Screening experiment of 10 mL scale cultivation was conducted with 64 modified SOT media containing each micronutrient combinations, and the cell growth was measured by spectrophotometric measurement (λ=664 nm) for 14 days. After then, eight media were selected for comparison of scale-up growth performance and biochemical differences in 20 L scale culture condition for 1 month. In 10 mL scale cultivation of screening experiment, culture medium containing mixed components of M and V (M+V) with cells showed highest absorbance, followed M+Z+V and M+Z+F combinations. In 20 L scale-up cultivation, the highest final biomass production and specific growth rate of S. maxima were recorded at single Z and followed mixed M+Z combinations media. In biochemical analysis, protein level of S. maxima cultured in mixed M+Z combination medium was significantly higher than others (p<0.05). Chlorophyll-a and C-phycocyanin of photosynthetic pigments were significantly increased in culture media containing single Z and mixed M+Z+V combinations (p<0.05). These results indicated that M and Z in JMS have significant effects on cell growth and biochemical compositions of S. maxima.