In conventional flotation, the sodium oleate is used as a collector for phosphate separation from silica. However, most of the phosphate deposits contain carbonate impurities, which deteriorate the flotation selectivity using sodium oleate. In this paper, the amenability of the carbonate separation from a sedimentary phosphate ore through bio-flotation process, as a one of various efforts to solve the carbonate problem, was tested. The interaction of two types of bacteria (Corynebacterium-diphtheriae-intermedius, CDI, and Pseudomonas aeruginosa, PA) with sodium oleate was investigated. The interaction between collector and bacteria was determined by Fourier Transform Infra-Red (FTIR) measurements, zeta potential before and after adsorption of bacteria, as well as frothing power. The results showed that bio-flotation could produce a phosphate concentrate of 0.85% MgO and 30.2% P 2 O 5 with a recovery of 92% at pH 5.5, 1.25 kg/t sodium oleate, ≥ 1 × 10 8 cells of CDI bacteria. The specification of such concentrate could not be obtained by the conventional flotation experiments, in absence of bacteria, under similar conditions. This means that bacteria could play a significant role as a surface modifier due to its selective adsorption onto the mineral surface as well as its interaction with collector.