Fed-Batch Bioproduction of Spectinomycin
25
500
400
200
100
......
' ~ ' ~ ' '
'
750 1250 1750 2250 2750 3250 3750 4250 4750
Glucose Feed Concentration (arbitrary units)
Fig. 8. Evidence of bi-modal maxima in spectinomycin bioproduction [48]
Therefore, depending on the glucose feed concentration, the two intermediate metabolites, 1,3 myo-inosadiamine and actinamine, or both, determine the
rate and the total amount of spectinomycin synthesized. Only a more detailed
investigation will reveal which pathway is favored for a given glucose feed
concentration. Nevertheless, certain qualitative inferences can be made about
the mechanism of spectinomycin biosynthesis based on the available information.
6 Exponential Structure for Mechanistic Model
Spectinomycin synthesis begins after a lag phase of about 24 h. As synthesis
continues its concentration increases quickly and saturates at the first level.
Later its concentration increases once again and saturates at a second higher
level. We interpret this profile in the following simplistic manner. When the
microorganism is moving out its growth phase, some bio-signal triggers or
activates the beginning of spectinomycin synthesis. The metabolic activity of the
microorganism then gradually switches over to the synthesis of spectinomycin
25
500
400
200
100
......
' ~ ' ~ ' '
'
750 1250 1750 2250 2750 3250 3750 4250 4750
Glucose Feed Concentration (arbitrary units)
Fig. 8. Evidence of bi-modal maxima in spectinomycin bioproduction [48]
Therefore, depending on the glucose feed concentration, the two intermediate metabolites, 1,3 myo-inosadiamine and actinamine, or both, determine the
rate and the total amount of spectinomycin synthesized. Only a more detailed
investigation will reveal which pathway is favored for a given glucose feed
concentration. Nevertheless, certain qualitative inferences can be made about
the mechanism of spectinomycin biosynthesis based on the available information.
6 Exponential Structure for Mechanistic Model
Spectinomycin synthesis begins after a lag phase of about 24 h. As synthesis
continues its concentration increases quickly and saturates at the first level.
Later its concentration increases once again and saturates at a second higher
level. We interpret this profile in the following simplistic manner. When the
microorganism is moving out its growth phase, some bio-signal triggers or
activates the beginning of spectinomycin synthesis. The metabolic activity of the
microorganism then gradually switches over to the synthesis of spectinomycin