The Study Of High Cell-density Mixotrophic Culture Of S.platensis

Spirulina are unicellular, filamentous bule-green algae or cyanobacteria. They have large quantities protein source, which is up to 60%-70%,eight balanced amino acids which man and animals can't synthesize, vitamins, multiunsaturated fattyacids, carbohydrates, microelements and so on ,which have five functions such as antifatigue, antianoxia, immune-regulate, regulation of blood fat and antineoplastic. Now Spirulina is applied to many fields such as food, cosmetic, medication, feedstuff, so Spirulina is a kind of multifunctional production with much potential value of empoldering and utilizing.Mixotrophic culture is a new method for culturing Spirulina in light with organic compound as supplementary carbon source, which can enhance the cell yield of Spirulina. Comparing with phototrophic culture and heterotrophic culture, mixotrophic culture can't influence the inducement synthesizing of pigment but improve the cell concentration of Spirulina, so mixotrophic culture has the potential and particular value in large scale culture. But mixotrophic culture has't come true in commercial production up to the present, it is very important to study the high cell-density mixotrophic culture of Spirulina.The strain of Spirulina is very important in the culture, so we filtrate the best strain S₂ from three strains S₁,S₂, S₃ via the experiments of phototrophic batch culture and mixotrophic batch culture, and detected the empoisoning of the used medium. In the end we found no fomite, so it is highly advantageous to culture. In order to offer directive parameters, the effection of of glucose on the mixotrophic batch culture of Spirulina was carefully studied. The oxygen of output in phototrophic culture is much more than the input in the heterotrophic culture, the active high concentration oxygen bring out free radical O₂^- to a great extent, which is tremendously devastating. In order to avoid the high concentration oxygen , the effection of three antioxidants : Na₂S₂O₃, Vc, Cys was studied , the results showed that 3.0g/l Na₂S₂O₃ is the best, and the maximum dry weight is up to 2.42g/l.The effects of three substances which are carbon source NaHCO₃, nitrogen source NaNO₃, phosphorus source K₂HPO₄ on the cellular growth of Spirulina and the optimized dosages were studied via single factor and orthogonal experiment, it showed that NaHCO₃ 8.4g/l, NaNO₃ 2.0g/l, K₂HPO₄ 0.1g/l can demand the three elements of carbon, nitrogen and phosphorus in mixotrophic batch culture of Spirulina ,so it is economical comparing with traditional Zarrouk medium.Fed-batch culture in five-litre-fermentor was studied to validate the effection of antioxidant Na₂S₂O₃ in mixotrophic culture, it showed that the maximum dry weight is up to 11.05g/l appending certain antioxidant comparing with 6.45g/l without antioxidant after ten days mixotrophic culture, the former is 1.87times as much as the latter; But the maximum dry weight is 1.76g/l,which is much smaller than 11.05g/l. It showed that mixotrophic culture can greatly improved cell yield of Spirulina and also showed the effection of antioxidant.