Studies On Culture Methods And Safety Of Chromium-rich, Iron-rich, Zinc-rich Spirulina Platensis

Chromium, iron, and zinc are essential trace elements, while their inorganic formscan not easily be absorbed. They have universal food value only after biotransformation.Spirulina is a kind of economic algae with high nutritional value and bioaccumulationability. This paper selected Spirulina platensis to investigate the culture methods ofchromium-rich, iron-rich, and zinc-rich spirulina. In order to provide a theoretical basisfor further commercial production, flatbed photobioreactor was used to explore thepossibility of large-scale cultivation of trace elements riched Spirulina platensisoutdoors. The nutrition and safety of Spirulina platensis riched with chromium, iron, orzinc is closely related to its supplementary amount, thus it is necessary to investigate thesafety of chromium-rich, iron-rich and zinc-rich Spirulina platensis as a functional food.From the point of production practices, we explored the culture methods ofchromium-rich, iron-rich, zinc-rich spirulina and its safety. The main conclusions are:（1）100mg/L following concentrations of CrCl₃·6H₂O had no significant effect onthe growth of Spirulina platensis.When the added concentration of CrCl₃·6H₂O was50mg/L or100mg/L, the chromium content in biomass reached to4.349mg/g,6.148mg/g.50mg/LCrCl₃·6H₂O had no significant effect on the growth of cells when addedin the logarithmic growth phases.（2） The effect of FeSO₄·7H₂O on the growth of Spirulina platensis and the ironcontent in biomass were closely related to its concentrations.The growth of Spirulinaplatensis was inhibited when the iron ion was deficiency, and50mg/L FeSO₄·7H₂O hadno significant impact on the growth of Spirulina platensis, while it would affect the ironcontent in biomass.（3）100mg/LZnSO₄·7H₂O had apparent inhibition effect on the growth ofSpirulina platensis, at the same time the cells had serious filaments break. The zinccontent in biomass with added ZnSO₄·7H₂O concentration of50mg/L or100mg/L,reached to1.471mg/g dry weight or3.317mg/g dry weight. These levels were higher（28.6and66.9times, respectively） than that of the cultivation with0.22mg/LZnSO₄·7H₂O.50mg/L ZnSO₄·7H₂O had no effect on the normal growth and filamentsform of the cells when added in the logarithmic growth phase.（4） Flatbed photobioreactor with a thickness of10cm, volume of250L was usedto culture chromium-rich, iron-rich, zinc-rich Spirulina platensis. The addition of metalsalts （CrCl₃·6H₂O:50mg/L; FeSO₄·7H₂O:40mg/L; ZnSO₄·7H₂O:50mg/L） had nosignificant impact on the growth of S.platensis, and the highest content of traceelements in biomass were Cr:6.524mg/g; Fe:3.758mg/g; Zn:0.624mg/g.（5） Toxicological experiments with mice showed that chromium-rich Spirulinaplatensis had no acute toxicity.30-day feeding experiments showed that1600mg/kgchromium-rich Spirulina platensis had no significant effect on mice; while3200mg/kgchromium-rich Spirulina platensis and1600mg/kg iron-rich Spirulina platensis were surmised to have a potential liver toxicity or renal toxicity on mice, but needed to befurther confirmed.1600mg/kg and3200mg/kg zinc-rich Spirulina platensis had noliver toxicity or renal toxicity on mice.