bioreactor studies of heterologous protein production by ...

3.12. Composition of Culture Media
The cuiture media employed in this study are briefly summarized as foilows:
1 YNF3 seiective minimal medium: 6.7 g/L yeast nitmgen base (YNB. wlo amino hds),
20 g/L glucose and 40 mg/L histidine (Nunberg et aL, 1988).
II. Maitose selective mimmal medium: 6.7 g/L yeast nitrogen base (W. w/o amino
acids), 20 g/L maltose, 40 mgL histidine and 40 m& lysine.
m. YPG nonselective cornplex medium: 5 g/L yeast extract., 10 g/L peptone, and 20 g/L
glucose (Bamett et al., 1983).
IV. YNB selecave solid agar medium: YNB selective minimal medium plus 20 g/L agar.
V. Maltose seletive solid agar medium: Maltose selective minimal medium plus 20 g/L
agar.
VI. YPG nonselective solid agar medium: YPG nollse1ective complex medium plus 20 gR.
aga
3.2. Strain Screening under Double Sdection Pressure
The original saain obtained from ATCC was maintained on the slants of YNB selective
solid agar medium (medium IV). This YNB selective medium does not contain leucine.
Since the host ceiI strain C468 is S. cercvisiae with autotrophic marker for leucine, it can
not grow without leucine supplementation. The plasmid pGAC9 contains a section of
LEU2 gene that encodes the enzyme for leucine synthesis. Oniy the piasmid bearing cells
cm grow on the YNB seleFtive medium. However, the YM3 slective medium confea
only one selection pressure. Under tbis selection presson, the glncoamyIase gene cm be