The Influence Of Culturing Mode On The Growth And Carbon Sequestration Of Spirulina Platensis

With fossil fuel combustion and vehicles exhaust emission, massive emissions of CO2-based greenhouse gases causing global warming intensifies and a series of environmental problems, which are threatening human survival and development. Therefore, more and more domestic and foreign researchers have payed much attentions to lower CO2 emissions. At present, there arises various CO2 emission reduction technologies, mainly including chemical, physical and biological methods. Microalgae has its unique advantages in the CO2 emission reduction, in terms of microalgae of breeding fast, small footprint, high rate of carbon sequestration. Otherwise, the growth and carbon sequestration were influenced by CO2 concentration, temperature, photoperiod, light intensity, training methods and organic carbon, etc. On the basis researchs of organic carbon source and light period, the research studied on the effects of CO2 concentration and light intensity,the different carbon sources and culturing modes,and different adding modes of carbon sources on the growth and carbon sequestration of Spirulina platensis. Finally, continuous cultivating Spirulina platensis for the study of growth and carbon sequestration was carried out(10 L) in a "photoautotrophic(CO2)- heterotrophic(glucose)" of reactor. The main conclusions of this paper are as follows:(1)To improve the specific growth rate and CO2 fixation rate of Spirulina Sp. the research was divided into four growth period:lag phase,the early of log phase,the end of log phase,the stable phase.The purpose was to optimize two main environmental factors which are light intensity and CO2 concentration. Experimental results showed that the growth of Spirulina Sp. was conditioned in a 1 L conical flaske under 25.0±1 ℃ and 16/8 of light period: the optimum condition of lag period is light intensity 3000 Lux,without bubbling the CO2;the optimum condition of the early of log phaseis was light intensity in 4000 Lux,with bubbling 15% concentration of CO2; the optimum condition of the end of log phase is light intensity in 5000 Lux,with bubbling 15% concentration of CO2; the light intensity of the stable phase is lower than 4000 Lux, CO2 was not essential. In continuous chltivation Spirulina Sp., culture conditions optimising experiments were individed into 4 four periods,the maximum biomass and carbon fixation rates were higher than the control group, which were 4.126 g/L and 58.231 mg/ Lh respectively.(2)This paper studied the impact of three carbon sources which were CO2, NaHCO3 and glucose on growth of Spirulina Sp.. It showed a certain concentration of CO2 as a carbon source, the highest biomass could reach to 1.287 g/L, better than Na HCO3 of 1.118 g/L. Although the group with glucose as carbon source after 72 h culturing, the maximum biomass could be 1.181 g/L. But the biomass was mere 0.247 g/L at the end of the culturing. So the group with CO2 as the inorganic carbon was more conducive to their growth. Research of three training methods(autotrophic、heterotrophic and mixtrophic)affected Spirulina Sp. of growth and carbon sequestration. It obtained that the biomass and carbon sequestration rate was up to 1.612 g/L and 105.431 mg/(L?h) under the mixtrophic cultivation of Spirulina Sp.. The light intensities of delay phase and the logarithm phase were setted at 3000 Lux and 4000 Lux in light culture conditions, respectively. And the light culture stage was bubbled 5% CO2 into the media. The first day and third days of the initial dark culture were added to 1g/L glucose.It showed that mixtrophic is more conducive to the growth and carbon sequestration of Spirulina Sp..(3) The different dosing modes of carbon sources affected Spirulina Sp. of growth and carbon sequestration in autotrophic-heterotrophic mode. The research showed that the group with supplementing 5% CO2 achieved the highest carbon sequestration rate and maximum biomass, in autotrophic stage, which could reach to 265.455 mg/(L?h) and 2.007 g/L, and were significantly better than adding 16 g/L of Na HCO3. The maximum biomass was only 1.648 g/L. In Autotrophic phase, the experimental groups were dosed different concentrations of organic carbon source-glucose. It found that autotrophic phase of organic carbon concentration was too high, which was not conducive to the growth and carbon sequestration of Spirulina Sp..The biomass and carbon sequestration rate was only 1.637 g/L and 197.553 mg/(L?h). In the process of heterotrophic, supplemented with 5% concentration of CO2 showed that the medium of p H decreased rapidly, and were not conducive to the accumulation of biomass and carbon sequestration of Spirulina Sp.. The biomass and carbon sequestration rate was only 1.501 g/L and 189.870 mg/(L?h). It would restrain the growth of Spirulina Sp., while the inorganic carbon and organic carbon existed in the autotrophic and heterotrophic respectively.(4) It was performenced to culture Spirulina Sp. in the reactor setting as "photoautotrophic(CO2)-heterotrophic(glucose)" cultivation model. The adding modes of different carbon sources affectted the growth and carbon sequestration of Spirulina Sp.. The results indicated that, in the light culturing phase and dark culturing phase, the groups were filled with 5% CO2 and appropriate amount of organic carbon-glucose, respectively, which was more conducive to the growth and carbon sequestration of Spirulina Sp..Otherwise the light culturing medium was filled into 5% CO2 in every 8 h and dark culturing medium was dosed with 8.5 g glucose, in 1st day and 3th day at the beginning of dark culture. The biomass and carbon sequestration rate decreased by 0.115 g/L and 76.887 mg/(L?h).Therefore, to reduce the impact of inorganic carbon source on dark culturing of respiration and organic carbon on light culturing of photosynthesis, in the light culture stage, inorganic carbon- CO2 should be dosed into medium for the growth of Spirulina Sp., based on the different growth stages, the medium should be dosed with the appropriate amount of organic carbon-glucose,which were more conducive to growth and carbon sequestration of Spirulina Sp..