Fig. 1

VHH production and growth parameters estimated from chemostat cultivations and corresponding model-based predictions for retentostat cultures. Aerobic, glucose-limited chemostats for parameter estimation were operated at 7 different dilution rate setpoints (D = μ) ranging from 0.015 to 0.170 h⁻¹. Shown are A the biomass-specific VHH secretion rate (q_P) and B the maintenance energy requirement (m_S) as well as the maximum theoretical biomass yield (Y_XS^max) in relation to μ. The dynamics of m_S and Y_XS^max were estimated by linear regression analysis on moving windows of the specific glucose uptake rate (q_S) as determined from three different consecutive dilution rates and at least two individual cultivations per dilution rate setpoint. C Model-based predictions for retentostat cultivations of the biomass built-up (Cx), the glucose concentration in the feed (C_S), µ, q_S, as well as D the VHH concentration in the supernatant (C_P) and q_P were calculated based on the average m_S and Y_XS^max values returned from the three sets of q_S-vs-μ relations for μ ≤ 0.100 h⁻¹ from (B)