Useful as host cells for expressing the recombinant protein, a method of selecting a cell with zero fucose level. Method, (d-) introducing a genetic mutation by contacting the cell with a population of CHO cells to methotrexate (MTX), a population of CHO cells comprising (e) mutant cell, non-toxic fucose binding agent When, the fucose-binding agent, comprising contacting a sufficient time to bind to a fucose moiety on the cell membrane of a cell population, step the time is the time which does not permit killing of cells; and (f) from a population of cells comprising a mutated cells to remove subpopulation of cells binding to fucose binding agent, whereby a step of selecting cells useful as host cells for expression of recombinant proteins, are selected manufacturing method cells comprising the step of having a Zerofukosu content. Also disclosed are useful for cells and cell lines as host cells for expressing the recombinant protein.