Study On The Optimization Condition Of Microbially Induced Calcium Carbonate Precipitation Through The Algae-bacteria Co-culture System

Microbially induced carbonate precipitation,an eco-friendly and energy-efficient technology,has attracted great attention worldwide.A variety of microorganisms including bacteria,fungi,and algae are capable of inducing carbonate precipitation through many biological pathways,but there are few investigations mainly focused on the induced deposition by the mixed cultivation of microalgae and bacteria.In this study,a co-culture system of Chlorella sp.and Sporosaricina pasteurii was constructed artificially to explore the synergistic feasibility of algal-bacteria interaction for induced deposition,and to provide theoretical basis for microbial induced deposition and new clues for biological species in induced deposition.In this paper,Chlorella sp.(NCU1)which was isolated from freshwater and Sporosarcina pasteurii ATCC 6453 as experimental materials to study the feasibility and the effects of different inoculation volume ratios,different initial pH and different glucose concentrations on the growth of microorganisms in the co-culture system.The effects of different initial pH,different rotating speeds and different calcium ion concentrations on the mono-culture sp.or S.pasteurii and the co-culture of Chlorella sp.and S.pasteurii were further discussed based on the results with the different growth conditions,and the exponential model was to fit the process of the deposition,and the product in the three culture systems was analyzed by scanning electron microscope(SEM),X-ray diffraction(XRD)and Thermo-gravimetric analysis(TGA)to explore the difference in product structure.The characteristics of extracellular polymer substance(EPS)were discussed preliminarily by using the acid base titration,Fourier transform infrared spectrum(FITR)and High-performance liquid chromatography(HPLC)in this paper,and the contents of the protein and polysaccharide in the EPS were also studied.The effect of microbial growth with different culture conditions in the algae-bacteria culture system was discussed.The results showed that under optimal growth conditions of algae-bacteria inoculation volume ratio of 3:2(v/v),initial pH value of 9.0 and glucose concentration of 1g/L,the Chlorella sp.biomass in the co-culture system was significantly improved by 37.74%,and the algae could grow well with bacteria.The effects of induced deposition with different condition in the co-culture system were discussed.The results showed that the optimum condition of calcium ions deposition was 5.0 of initial pH,0 of rotating speed and 500 mg/L of Ca2+ concentration in the algal-bacteria culture system.And the change curves of calcium ion concentration in the different culture systems under different conditions were in line with the exponential model,and R2 values were different but all above 0.9.The maximum value of k was 0.6059,and in the condition of the calcium ion concentration was 250 mg/L,the rotating speed was 0 and the initial pH was 5.0 when in the co-culture system,which indicated that the low concentration of Ca2+could improve that the process of induced position.The mineral substances induced by three different culture systems were analyzed by SEM,XRD and TGA,and the crystalline mineral particles were calcium carbonate calcite,but the shape and size of the products in each culture system were different.Moreover,the pyrolysis temperature of mineral particles in the algal-bacteria co-culture system was 703.92?,which was higher than 213.92?,47.63? and 175.92? when compared with algal group,bacterial group and calcium carbonate group.The results indicated that the minerals in the co-culture system may have better crystal structure and crystallization degree.The lost mass of mineral particles in the co-culture system was 38.12%,and the residual mass was 61.88%,which was similar as loss and rest of proportion of standard CaCO3 by thermal decomposition,and confirmed that the product of the algal-bacteria co-culture system was CaCO3.The characteristics of extracellular polymer substance(EPS)were discussed preliminarily,and the results showed that the contents of dissolved extracellular polysaccharide and protein in the three different cultivation system were:algae-bacteria>bacteria>Chlorella sp.Furthermore,the components of EPS in the three culture systems were analyzed by acid-base titration,FITR and HPLC.The results showed that EPS in these three culture systems all contained typical functional groups such as hydroxyl group and carboxyl group,and glucose,mannose and galactose,whose components were complex and mainly consisted of proteins and polysaccharides.