Abstract: The invention provides an isolated thermostable polypeptide possessing FGF2 activity and having at least 85% sequence identity to SEQ ID NO: 2 (FGF2 wt) or a functional fragment thereof, and comprising at least one amino acid substitution R31L and the use thereof in the cell biology research, regenerative medicine and related medical applications or cosmetics. Further it discloses a culture medium comprising subjected FGF2 suitable for culturing a human pluripotent stem cells involving both human embryonic stem cells and induced pluripotent stem cells.