The Thermodynamic Analysis And Application In The High Density Fermentation Of Recombinant Escherichia Coli

With the thermodynamic method and the feed-batch cultivation technics, the purpose of this paper was to frame an optimal temperature control strategy which was suitable to the Recombinant Escherichia coli constructed in our lab. We discussed the optimal temperature control policy in the growth phase and the inducing phase. The reason of the expression of poly-collagen in the high density fermentation was analyzed. The work of this paper opened a new way to obtain the optimal temperature operating parameter in the fermentation.The power-time curves for the growth of two strains of Recombinant Escherichia coli (BL 21 3.1, BL 21 3.7) at different temperatures have been determined by using Micro DSC III. On the basis of the generalized logistic equation, a power-time curveequation, , was proposed to describe the power-time curves in the growth phase, and the growth rate and fungistatic rate constantsμ,γwere fitted. Alinear model, , was proposed to describe the power-time curves in the inducing phase. The nonlinear equations ofμ-T were also established for deciding the optimal temperature of growth corresponding to the maximum values ofμ.For BL 21 3.1, we gainedμ= -0.0001T² + 0.0057T² - 0.1596T + 1.4598T_opt = 34.1896℃For BL 21 3.7, we gainedμ= -0.0001T³ + 0.0053T² - 0.1491T +1.3654T_opt = 34.3952℃The results indicated that below the inducing temperature, the growth of recombinant Escherichia coli (BL 21 3.1, BL 21 3.7) was perfectly fitting the Logistic equation; when the culture temperature was set at or above the inducing temperature, the growth didn't fit the Logistic equation and it was suitable for us to use the linear equation to describe the inducing growth. In order to get the maximum collagen production, for BL 21 3.1, the control temperature should be set at 34.2℃in growth phase, the inducing temperature should be set at 42℃; for BL 21 3.7, the control temperature should be set at 34.4℃in growth phase, the inducing temperature should be set at 42℃Complied to the temperature control strategy, we cultivated the recombinant Escherichia coli (BL 21 3.1, BL 21 3.7) in the bioreactor. The reason of the expression of poly-collagen in the high density fermentation was analyzed, we got the conclusion that the high effective expression was the footstone of the aggregation of the collagen monomer.