Abstract

Recombinant Escherichia coli BL21 was used to produce human-like collagen in fed-batch culture. After building and analyzing the kinetic models of fed-batch cultures, the maximum specific growth rate, Y_x/s and Y_p/s were 0.411 h^-1 , 0.428 g·g^-1 and 0.0716 g/g, respectively. The square error of cell growth models, glucose consumption model and human-like collagen formation were almost all around 94%, which indicated that the kinetic model could describe the actual change well. According to the target, that is, to gain the highest productivity of human-like collagen, the feeding rate (F) was worked out on the basis of Pontryagin's minimum principle. In the verification experiments, the specific growth rate was controlled at 0.15 and 0.04 h^-1 at the fed-batch and induction phase, respectively. The result showed that the concentrations of cell and human-like collagen could reach 87.6 and 6.11 g·L^-1, and they were raised by 17.9 and 18.6%, respectively.

Key words: Fed-batch culture, human-like collagen, maximum specific growth rate, Pontryagin's minimum principle, recombinant Escherichia coli.

Abbreviation

, Glucose concentration, g·L^-1; P, human-like protein density, g·L^-1;S_F, flux glucose concentration, g·L^-1; t, time, h; t₀, the starting time, h; t_f, the final time, h; J, the goal function; λ(t), Covariant vector; H, Hamilton function; Y^*_x/s,apparent yield, overall stoichiometric cell yield coefficient (grams of cell substrate consumed per gram of cell), g·g^-1; Y_p/s, product yield coefficient, g·g^-1;  μ, specific growth rate, h^-1;  μ_max, the maximum specific growth rate, h^-1; σ, specific rate of substrate disappearance, h^-1;  π, specific rate of product formation, h^-1; α, yield coefficient of collagen accumulation rate associated with cell growth rate, g·g^-1; β,variable macrokinetic parameter, yield coefficient of collagen accumulation rate associated with cell growth rate, g·g^-1·h^-1.