Metabolic engineering of Bacillus subtilis for the efficient biosynthesis of uniform hyaluronic acid with controlled molecular weights

► Two artificial operons carrying PmHAS and precursors genes consist expression system. ► A novel two-stage induction strategy was established according to constructed system. ► Hyaluronic acid accumulated 6.8 g/L in shake flask by expressing GlcUA independently. ► Sizes of hyaluronic acid can be controlled by time of induction of precursors and HAS. ► Uniform hyaluronic acid of varying sizes gained here all reached considerable yields.