bioreactor studies of heterologous protein production by ...

7.1. Conclusions
CHAPTER 7
CONCLUSIONS AND RECOMMENDATIONS
Fundamental engineering studies were carried out on protein production by f ~ e
suspension and immobilized celis of a recombinant yeasL S. cerevisiae C4681pGAC9.
Baszd on the results obtained. the foiiowing conclusions may be dnwn.
1. Batch culture studies indicated that in the YPG nonselective medium, the recombinant
yeast undenuent diauxic growth and the recombinant protein production was growth-
~ssociated. The recombinant protein yield (units of glucoamyiase. per gram cells) was
correlated with specific growth me. The recombinant protein yield decreased with
increasing specific growth rate. This is possibly due to an increased piasmid copy number
or land an increase in DNA transcription efficiency as a result of the reduced S ~ ~ C
growth rate.
2. The importance of metabolic pathways in yeut with regard to recombinant protein
formation was analyzed. Production of glucoamylase was shown to be associated with
oxidative growths of the recombinant ymt (both glucose and ethano1 oxidation
pathways). In order to produce recombinant protein efficientiy the TCA cycle mut
function actively shce the T'A cycle provides the intemediates ~quired for protein
synthesis. At high glucose level, secretion of the recombinant protein was repressed