Abstract: Isolated strains of supercapsulated streptococci band at a density of no greater than 1.03 g/cm3 in a Percoll gradient and are capable of producing hyaluronic acid with molecular weight exceeding 6 million Da. Methods of producing high molecular weight hyaluronic acid employ a supercapsulated strain of streptococcus which bands at a density of no greater than 1.03 g/cm3 in a Percoll gradient. Methods of selecting streptococcus strains capable of producing hyaluronic acid with a molecular weight exceeding 6 million Da comprise, inter alia, cultivating supercapsulated strains of streptococci which band at a density of no greater than 1.03 g/cm3 in a Percoll gradient.

Abstract: A method for selecting streptococcus strains capable of producing hyaluronic acid with molecular weight exceeding six million includes the steps of cultivating strains of streptococci individually in culture medium which is free of metal ions which promote degradation of hyaluronic acid and which does not release from the reactor metal ions which promote the degradation of hyaluronic acid; and selecting a supercapsulated strain of a streptococcus, supercapsulated members thereof having a mucoid morphology and being capable of forming capsules having a diameter of greater than 4 &mgr;m.