Study On The Strain Selection And Main Growth Properties Of Spirulina Platensis

In this thesis, Spirulina platensis was study about its strain selection and growth properties. The main aspects and results are as follows:1 The strain selection of S. platensisThe high-yielding strain S. platensis with a output of above 12gm^-2.d^-1 was selected from various Spirulina species in terms of growth rate. The S. platensis had a good resistance to stress, for instance, extreme temperature, strong irradiation and high salinity. The liquid medium were adopted to preserve the S. platensis at the conditions of ordinary temperature and weak light.2 The optimal culture conditions for S. platensisThe Zarrouk medium were used to study the optimal culture condition for S. platensis. The optimal parameters were: NaHCO₃ 10g/L, NaNO₃ 2.0g/L, pH 8.5-10.5, 30°C and 4500 lux. The maximum growth rate 0.32 O.D.d^-1 was obtained at the aforementioned culture conditions.3 The applications of essential trace elements in the culture of S. platensisA different amount of Zn²⁺ ,Se⁴⁺ , and Ge⁴⁺ were added into the culture medium in which the S. platensis were cultured to study the effects of these trace elements on the growth of S. platensis and the contents of these trace elements. The experiments showed that the growth rate of S. platensis weren" t affected by 3mg/L of Zn²⁺, Se⁴⁺, and Ge⁴⁺, and the contents of these trace element were significantly higher than the controls. When 3mg/L Zn²⁺, Se⁴⁺, Ge⁴⁺ were separately added into the culture medium, the contents of Zn , Se and Ge were 462 , 7.82 and 4.36ug/g respectively.4 The effects of heavy metals on the culture of S. platensisIn the culture of S. platensis, the heavy metal elements Pb , As and Hg demonstrated strong toxicity to S. platensis and substantially existed in the S. platensis. The growth was inhibited by 2mg/L Pb²⁺ or As³⁺ . The S. platensis were killed by 0.2mg/L Hg²⁺ in several minutes. When 0.2mg/L Pb²⁺, 0.2mg/L As³⁺ and 0.06mg/L Hg²⁺ were separately added into the culture medium, the contents of Pb , As and Hg in the S. platensis were 3.21 , 2.10 and 0.54 μg/g respectively.