Optimization For CO₂ Fixation Using Spirulina And Preparation Of Phycocyanin

With the rapid development of the economy,the large-scale use of fossil energy such as petroleum and coal,and the emitted large amount of greenhouse gases such as carbon dioxide have led to the deterioration of the global ecological environment.Therefore,the reduction and reuse of carbon dioxide has attracted widespread attention.Microalgae has the advantages of high photosynthetic efficiency and fast growth rate.The use of microalgae to fix carbon dioxide is not only safe and efficient,but also can produce high value-added microalgal products,so it has a good development prospect.As one of the world's most important economic microalgae,despite of that Spirulina has a fast growth rate and matured large-scale cultivation in the Spirulina culture process.there are still some outstanding problems for CO₂ fixation using Spirulina,such as low carbon fixation efficiency and high production cost.In this study,the carbon dioxide utilization efficiency of the CO₂ carbon sequestration carbon-reactor currently used by major domestic Spirulina producers was firstly investigated.It was found found that the carbon sequestration carbon reactor currently used has different carbon dioxide reaction residence time(about 0.5?3 s),poor gas-liquid mixed mass transfer efficiency,large amount of CO₂ gas escape,resulting in low CO₂ utilization efficiency of about16%to 35%.The CO₂ conversion and utilization efficiency during the open large pond culture process is determined as about 86%.The flow field of the existing carbon-fixing reactor was simulated using simulation methods.On the basis of this,two kinds of novel reactors were designed as:liquid circulation type and gas circulation type reactors,to overcome the two key problems of low mixing intensity and short residence time.Compared with the existing carbon-fixed reactor,the carbon dioxide utilization efficiency of the improved carbon-fixing reactor is increased from the existing 16%?37%to 47%?51%,respectively,and the carbon dioxide utilization efficiency is effectively improved.In addition,Spirulina powder was used as raw material to improve the extraction and preparation process of phycocyanin from Spirulina,and develop low-cost and high-purity phycocyanin production process.Firstly,the algae crushing process was optimized,and the algae cells were broken according to the ratio of 1:20,and the dissolution rate of phycocyanin was up to 80%.At room temperature 25°C,the crude phycocyanin extract was obtained by centrifugation,and then partially soluble protein and chlorophyll components were removed by salting out with 25%saturation of ammonium sulfate.Subsequently,the phycocyanin crystal precipitation conditions were systematically optimized,and the optimal phycocyanin crystal precipitation conditions were obtained as follows:room temperature 25°C,the phycocyanin precipitation under 60%saturation ammonium sulfate was used as protein sample with protein concentration of 12 mg/m L,8%ammonium sulfate as precipitant,p H 7.At this conditions,food grade phycocyanin with A₆₂₀/A₂₈₀ of 1.7 can be obtained with the recovery rate as above95%.The crude phycocyanin obtained by precipitating 25%of ammonium sulfate obtained above is further purified by Hitrap phenyl Fast Flow hydrophobic chromatography to obtain high-purity phycocyanin with A₆₂₀/A₂₈₀ purity of 3.5,and the total recovery rate is about 40%.The investigation and design of the efficiency of carbon-fixing carbon-reinforcing reactor during Spirulina production process and the development of pharmaceutical-grade phycocyanin preparation process have laid a certain work for the large-scale promotion and comprehensive utilization of Spirulina carbon-fixing culture.