Hygromycin B is an antibiotic produced by the bacterium Streptomyces hygroscopicus which is commonly used as selective antibiotics in cell line transfection and cell selection. As a primary manufacturer of Hygromycin B, TOKU-E is the first company identified all the impurities in hygromycin B and tested the cell line toxicity of all individual impurity and found that one of the impurities are highly toxic to the cell lines. TOKU-E's high purity EvoPure^® line of antibiotics is virtually free from any and all impurities.