Influence of induction stages on tyrosinase production. The freshly transformed E. coli JM109 (pMFvpt) recombinant cells were grown in shake flasks at 37°C and induced with 1 mM IPTG at the early (from the beginning of the cultivation), mid (6 h cultivation) or late (8 h cultivation) growth phase. The extracts of E. coli JM109 (pMFvpt) were prepared and analyzed by SDS-PAGE. Lanes 1–4, samples from induction at the beginning of the cultivation; Lanes 5–8, samples from induction at mid-growth phase; lanes 9–11, samples from induction at late-growth phase. The arrow indicates the position of tyrosinase in the gel. Molecular weight standards are shown on the left.