Salt-tolerant Water Efficient Carbon-fixing Microalgae Breeding

There are more than 0.32 million hm² of saline-alkali land in Dongying City of Shandong province,and be increasing 1000-2000 hm² land each year.The new method of carbon sequestration and soil fertility was investigated in order to fixing carbon and reducing discharge and saline-alkali reclamation in this paper.The determining the optimal culture conditions and increasing the efficiency of carbon dioxide uptake rates were researched through the influence of the growth characteristics and biochemical components of microalgae which be cultivated by the soil soaking water of Dongying saline-alkali land in experiment condition.The main conclusions are as follows:?1?First,the soluble salt content in soil was analyzed,chlorine ion and sodium ion accounted for 91.3%of the total content.The soil was alkaline?pH 8.5-9?and the organic content was low(4.82 g kg^-1).According to the basic properties of the soil,two types of microalgae,S.platensis and P.cruentum,were selected.S.platensis's protein content is 46⁴8%,it can increase organic content of soil effectively;P.cruentum's polysaccharides is 31³4%.Its soluble polysaccharides can adsorb sodium ion effectively.?2?Culture S.platensis and P.cruentum with soil soaking water of Dongying saline-alkali and exploring the optimal culture conditions.Under appropriate conditions of 2.5 g L^-1 NaNO₃,0.5 g L^-1 K₂HPO₄,120?mol m^-2 s^-11 and 24 hr irradiance,and 3%CO₂ enriched gas aeration,the biomass of S.platensis reached 11¹2 g L^-1 after 15 days cultivation with the carbon fixation rate of 2.21 g L^-1d^-1.Under appropriate conditions of 0.3 g L^-1NaNO₃,0.02 g L^-1 NaH₂PO₄,120?mol m^-2 s^-11 and 24 hr irradiance,and 2%CO₂enriched gas aeration,the biomass of P.cruentum got 4⁵ g L^-1 after 15 days cultivation with the carbon fixation rate of 0.48 g L^-1d^-1.Soluble polysaccharides increase with the increase of light intensity and light/dark ratio,reaching about 2.0².5 g L^-1.?3?For decreasing the nutritive salt and insuring the microalgae growth well,simple medium prepared by adding NaNO₃,K₂HPO₄ or NaH₂PO₄,and CO₂ into saline soil water to culture S.platensis and P.cruentum.Nitrogen and phosphorous were absorbed completety by microalgaes.When NaNO₃ concentration was lower than 2.5 g L^-1,the concentration of protein in S.platensis cells were limited,about 18-25%,polysaccharides in S.platensis cells were promoted,about 20-30%;When NaNO₃concentration was lower than 0.27 g L^-1,the concentration of protein in P.cruentum cells were limited,about 18-25%,polysaccharides in P.cruentum cells were about 20-30%?4?Culturing S.platensis and P.cruentum with distilled water and saline-alkali soil?5:1?,to determining the influence of physicial and chemical properties of saline-alkali land in Dongying.With the culturation of S.platensis,the organic content of the soil was increased in 19.6 g kg^-1,the exchangeable sodium centent has a little change,about0.18 cmol kg^-1,the pH of the soil was 9 with 2.5 g L^-1 NaNO₃,0.5 g L^-1 K₂HPO₄,and3%?v/v?CO₂.For the P.cruentum,the organic content in the soil has a little change,about6.88 g kg^-1,the exchangeable sodium centent decreased in 0.10 cmol kg^-1,the pH of the soil was 8.3 with 0.27 g L^-1 NaNO₃,0.02 g L^-1 NaH₂PO₄,and 2%?v/v?CO₂.It can be see that the S.platensis could increase the organic content of the saline-alkali soil,and the P.cruentum could decrease the alkaline and the exchangeable sodium centent.Above all are showed that it is lay the new foundation to carbon sequestration and soil fertility for the saline-alkali soil by means of the S.platensis and P.cruentum which be cultivated through the soil soaking water of saline-alkali land.