This invention relates to a novel cell culture medium and methods to enhance recombinant antibody purity using the cell culture medium disclosed herein. The novel cell culture medium is a self-made feeding medium, which comprises from about 90 nM to about 500 mM cysteine, from about 50 mM to about 500 mM tyrosine, and from about 50 mM to about 300 tryptophan. This invention also relates to a method of growing cell culture using the cell culture medium disclosed herein By controlling the concentration of cysteine in the self-made feed medium as well as the amount and time of adding this feed medium into the cell culture, the purity of antibodies is significantly improved while glycosylation profile and antibody expression level are consistently maintained to guarantee the efficacy of antibodies.