The exploitation of dynamic process conditions increasingly finds attention for strain screening and bioprocess development of biotechnological products. Prerequisite for successful dynamic experimentation is the controlled deflection of process parameters, e.g. temperature, pH or specific substrate uptake rates, while the latter can be considered the most challenging. Here, a soft-sensor based control strategy capable of dynamic control of specific uptake rates is presented, opening new perspectives for efficient process development. A soft-sensor on the basis of a redundant equation system involving the Degree of Reduction (DoR) and Carbon (C) balance was used for the estimation of the real-time biomass concentration and used for closed-loop control of specific uptake rates using a mass balance based control approach. The power of the presented soft sensing approach for bioprocess development was demonstrated on microbial bioprocess development tasks: (a) the control of the specific substrate uptake rates in a non-induced E. coli decellerostat culture aiming at the determination of the specific acetate production as a function of the specific substrate uptake, (b) the static control of the specific substrate uptake rate in an induced P. Pastoris AOX expression system, (c) the dynamic control of specific substrate uptake rates under induced conditions in a E. coll PET expression system and (d) the simultaneous dynamic control of the specific glucose and arabinose uptake rates in an E.coli pBAD expression system. In this contribution the dynamic controllability of multiple specific substrate uptake rates using a first-principle soft sensor independent of known or dynamically changing yield coefficients in recombinant bioprocesses is demonstrated for the first time. The presented control strategy holds potential to become a key process analytical technology (PAT) tool for bioprocess development. (C) 2013 Elsevier Ltd. All rights reserved.