Effects Of Immobilization On Physiology And Biochemistry Of Chlorella Vulgaris

With the development of social economy in China,the problem of water pollution is becoming more and more serious.The use of Chlorella vulgaris to purify sewage has aroused widespread interest.When using Chlorella vulgaris to purify sewage,immobilization is considered more economical and feasible method.It is a common method to optimize the conditions of immobilization according to the physical and chemical factors such as the difficulty of pelleting,adhesion,tailing,mechanical strength and substance transfer efficiency of immobilized pellets.However,is it the best condition for Chlorella vulgaris growth based on the physicochemical properties of gelatin spheres?In this paper,the effects of this traditional fixing method on the physiological and biochemical properties of Chlorella vulgaris were studied.And the immobilization conditions were optimized according to the physiological and biochemical factors of Chlorella vulgaris,and the responses of Chlorella vulgaris immobilized by different methods to stress were also studied.According to the physical properties of the colloidal spheres,the optimum immobilization condition of Chlorella vulgaris was 4%sodium alginate,4%calcium chloride,immobilizing for 3 hours,initial algae density 3.08*105 cell/mL.The specific growth rate of Chlorella vulgaris immobilized with this method decreased by 0.81/d in comparation with free Chlorella vulgaris,and sodium alginate was the main factor affecting the growth rate of immobilized Chlorella vulgaris.Similarly,this fixation method reduced Chlorella vulgaris net photosynthetic rate by 26%,and sodium alginate was also the main factor affecting the photosynthetic rate of immobilized Chlorella vulgaris.Taking the net photosynthetic rate of Chlorella vulgaris as the index,the optimum immobilization conditions were 3.5%sodium alginate,3%CaCl2,initial algae density of 2.05*105 cell/mL and immobilizing time of 2 h.In addition,the chlorophyll content and protein content of Chlorella vulgaris immobilized according to this method were also analyzed.Culturing free Chlorella vulgaris(F),traditional method immobilization Chlorella vulgaris(O)and new method immobilization Chlorella vulgaris(N)under 35‰ salinity or freshwater fish culture wastewater conditions respectively,both SOD activity and CAT activity were F<O<N,and the MDA content were F>O>N.It indicated that the immobilization increased the stress resistance of Chlorella vulgaris.In conclusion,when immobilizing the Chlorella vulgaris,the properties of immobilized gel balls were often used as an index to optimize the immobilization conditions.However,it was found that the physiological and biochemical properties of Chlorella vulgaris immobilized by this method were not as good as those of free Chlorella vulgaris.The physiological and biochemical properties of Chlorella vulgaris immobilized with new immobilization scheme were close to those of free Chlorella vulgaris,and its resistance to stress was also better than that of free Chlorella vulgaris and traditional fixed Chlorella vulgaris.