Optimization Of Culture Conditions For Spirulina And The Primary Studies Of Its Anti-tumor Effect

Spirulina were hailed as "the perfect food in the 21st century"and "the optimal health product in the 21st century" by FAO and WHO due to its nutritional value and the ability to produce valuable chemical compounds,such as protein,polysaccharide, unsaturated fatty acids,vitamins,etc.In recent years,there is a great market demand for Spirulina.The biomass was consideed as the sole indicator in the current culture, so the output of active ingredient is far from satisfying the needs of the market. Microalgal biomass and metabolites are close related to its culture conditions. Therefore,it is significant to optimize the cultural conditions of spirulina for realizing the high biomass and achieving nutritional ingredients from Spirulina for different purpose.The effects of medium,temperature,light intensity and phytohormones on the growth and the metabolites of protein,intracellular polysaccharide(IPS), extracellular polysaccharide(EPS),superoxide dismutases(SOD) were studied in a systematic way.At the same time,the anti-tumor effect of EPS,IPS and PC was preliminary studied.The results showed that,when the concentration of sodium bicarbonate,nitrogen sources,phosphate,and sodium chloride in the medium was proportioned as A(g/L)(18,2.5,0.5,1.0),B(14,2.5,0.5,0.5),C(10,2.5,0.8,1.5),D(18,2.5,0.2,1.5), the metabolites of biomass,EPS,IPS and protein in the Spirulina was as 0.69,0.49, 0.71,0.33 times those of original medium respectively.It was evident that the biomass,IPS,EPS and protein of Spirulina all increased outstandingly through optimization of the medium ingredient.It was found that the light intensity was at the range of 4000 lux to 5000 lux and the temperature was in the range of 30～35℃was the optimum condition for the growth of Spirulina.The optimum temperature and light for excreting of IPS were consistent with optimum condition for the growth of Spirulina.Illumination and temperture unsuitable for the gowth of Spirulina would raise EPS content and SOD activity.That is,high temperature and feeble illumination were favorable to the excreting of EPS.SOD activity was increased notably under the condition of low temperature and strong light.Lower concentration of phytohormones significantly promoted the growth and protein content of Spirulina,higher concentrations inhibited its growth but accelerated EPS and enhanced SOD activity. The optimized cultural conditions were ascertained,so as to provid the theory and practical parameters of scale-up exploitation protein,polysaccharides and SOD form Spirulina in the functional food and pharmacy.The antitumor function of IPS,EPS and PC by MTT assay indicated that the optimum dosage were 80μg/mL,100μg/mL,120μg/mL and the inhibition rates were achieved 47.92%,42.95%and 31.22%respectively.Caspase-3 activity was measured by Caspase-3 kit.Caspase-3 activity achieved to the highest,that was as 4.06,6.64, 5.70 times as the control group respectively at 36h,24h,12h after being added the IPS, EPS and PC.It can be inferred that the mechanism of antitumor effect of three extracts of Spirulina was through activating the Caspase-3 protease family,thus inducing cell apoptosis.