Recombinant protein production in Y. lipolytica
Upon transformation of the expression cassettes into Y. lipolytica
JMY1212 or JMY1165, ura-positive colonies were randomly selected
and grown at 28 C in 20 ml-flask YTD medium for 24 h.
These cultures were then used to inoculate fresh YTD medium
(20 ml) supplemented with 1.2 mM CuSO4 at an initial cell density
of OD600 = 0.2. After incubation at 28 C for 30 h under agitation
(135 rpm), culture media were centrifuged; the supernatants containing
the secreted proteins were recovered and subsequently
used for enzymatic assays or further purification steps. The effect
of copper ions (Cu2+) on the production of the laccase was also assayed
in JMY1212 strain by varying the concentration of CuSO4 in
the range 0–2 mM.