Optimization of medium components
TBSB was used as the initial medium for medium components optimization.
For carbon source optimization, 10 g/L glucose, fructose, xylose, and
sucrose were added into the TBSB medium to replace the original
glycerin. The cell growth and protein production using glucose carbon
source were used as control. For nitrogen source optimization,
additional 10 g/L urea,
(NH4)2SO4,
and NH4Cl was added
to the TBSB medium, and the protein yield and OD600 in
the TBSB medium were used as control. For all medium optimization
experiments, the cultivation and induction condition was set at the
optimal level previously determined.