| Dunaliella salina, a kind of microalgae with high commercial value, has been successfully cultivated in large scale. However, the technologies currently used to harvest D. salina cells have many shortages due to cells' frangibility and low cell density in culture liquid. Thus, in this paper, the cells hydrophobicity characteristics and cells density , key factors that affected the harvest efficiency, were studied, and the harvest of the cells by the method of micro-filtration without adding any filtration aids was investigated, then the reasons of leading to cells breakage were analyzed in hollow fiber micro-filtration process.The surface hydrophobicity of D. salina was measured by the method of xylene-water in every growth time. The results showed that the cells surface hydrophobicity increased to 90%, due to lacking nutritional ingredient in culture medium and cells changing into spore form, when cells gone into decline phase.The density of cells was measured by the method of pycnometer. With the growth of cells, the cells density was changed. In the initial logarithmic phase, the density was 1.11g·cm-3, and the density was changed into 1.07g·cm-3 in the telophase logarithmic phase. Due to the different growth phase, the ingredients in cells were also different, so this reason leaded to the change.The causes of D. salina cells harvest rate during the enrichment process with hollow fiber in the lower pressure were investigated. The results showed that membrane flux was determined by flow rate and the pressure. In a lower pressure, membrane flux was determined by pressure. The higher the pressure became, the more apparente the action of flow rate became.The cells breakage was discussed in the harvesting process. The results showed that breakage cells were from the salina suspension in filter process. The shear flow was the main reason for leading cells to broken, and the immediate cause was the shearing strength using cells in the salina suspension.
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