3.4.2 Enhancing P. pastoris metabolic activities in the successive
methanol induction phase
The major chemical reactions in heterogeneous protein by P.
pastoris and relevant key enzymes involved have been widely reported
previously.1,10 Functions of the key enzymes involved
in methanol metabolism were as follows: AOX catalyzes the first chemical
reaction in methanol metabolism
(CH3OH+O2→HCHO+H2O2);
FLD and FDH contribute to NADH and ATP regeneration ability in the
formaldehyde dissimilation pathway and the role of this path was to
supply a source of energy for heterogeneous proteins production. As
shown in Fig.4II, when using the “high DO-low glycerol concentration”
control strategy, specific activities of AOX, FLD and FDH were
significantly repressed, leading to a limited methanol/oxygen
consumption and hLYZ expression. As for the batch using the periodic DO
control strategy, the specific activities of AOX, FLD and FDH were
obviously enhanced. Accordingly, the average specific methanol
consumption rate and OUR increased for about 40% with the periodic
control strategy, which eventually led to an efficient hLYZ production.