| The metabolism of recombinant Escherichia coli BL21 containing a human-like collagen cDNA was investigated in this paper. Based on the metabolic flux analysis (MFA) technology, the metabolic flux distributions and energy balancing at the different specific growth rates were discussed. The optimum cultivation conditions before and after induction were determined respectively.1. Before induction, the fluxes flowed into the PP pathway was at its peak value when the specific growth rate was maintained at 0.16 h-1. At the meantime, the fluxes flowed into biosynthesis also reached the highest level. These could be illuminated that the anabolisms were at their highest levels whenμ=0.16 h-1. In addition, the flux flowed from AcCoA and OAA to Iscit increased only 0.87％and 1.04％when the specific growth rate was increased from 0.16 h-1 to 0.25 h-1; but the flux flowed into acetate pathway increased dramatically 110％and 25％. The optimalμthereby was confirmed at around 0.16 h-1 before induction.2. After temperature upshift, the percent fluxes flowed into the PP pathway increased first and decreased afterwards. The fluxes reached its peak values when theμ=0.05 h-1. Meanwhile, the flux flowed to Iscit increased 7％when theμadjusted from 0.05 to 0.07 h-1, whereas the acetate produced from AcCoA increased more than 29％. Consequently the citroyl synthetase can be considered reached its maximum limitation atμ=0.05 h-1.3. Before induction, the ATP consuming rates of biosynthesis were much less than mATP in 3 culture conditions while the total ATP fluxes increased from 47.83 to 80.96 mmol·g-1h-1. This can be accounted for the increase of ATP generating rate made slim contributions for the biosynthesis.4. After induction, more and more energy consumed in maintenance and futile cycles, this is uneconomical for the biosynthesis.
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