Model Predictive Feeding Rate Control in Conventional and Single-use Lab-scale Bioreactors: A Study on Practical Application

A developed solution for fed-batch process modeling and model predictive control (MPC), facilitating good manufacturing practice (GMP) based on process elaboration, control, and validation, is presented in the paper. The step-by-step evolution of the so-called “golden batch” optimal biomass growth profile and its control during the process is demonstrated. The case study of an advanced fed-batch control was performed on the recombinant E. coli BL21 lab-scale (5.4 L) biomass production process using the conventional stirred tank glass reactor. Additionally, a test experiment for control reproducibility and applicability assessment of the proposed approach was carried out in a single-use stirred tank reactor (5.7 L). Four sequentially performed experiments are demonstrated as an example for desirable feeding profile evolution for E. coli BL21 biomass production in a glucose-limited fed-batch process. Under different initial biomass and glucose conditions, as well as for different reference feeding profiles selected in the explorative experiments, good tracking quality of preset reference trajectories by the MPC system has been demonstrated. Estimated and experimentally measured biomass mean deviations from the preset reference value at the end of the processes were 4.6 and 3.8 %, respectively. Biomass concentration of 93.6 g L–1 (at 24 h) was reached in the most productive run. Better process controllability and safer process run, in terms of avoiding culture overfeeding but still maintaining a sufficiently high growth rate, was suggested for the process with biomass yield of 79.8 g L–1 (at 24 h). Practical recommendations on the approach application and adaptation for fed-batch cultures of interest are provided

Generation of narrow-band terahertz radiation via optical rectification of femtosecond pulses in periodically poled lithium niobate

We demonstrate a promising technique for generating narrow-band terahertz electromagnetic radiation. Femtosecond optical pulses are propagated through a periodically poled lithium-niobate crystal, where the domain length is matched to the walk-off length between the optical and THz pulses. The bandwidth of the THz wave forms is 0.11 at 1.7 THz. Optical rectification gives rise to a THz wave form which corresponds to the domain structure of the periodically poled lithium niobate. © 2000 American Institute of Physics.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/70975/2/APPLAB-76-18-2505-1.pd

Polarisation maintaining 100-W Yb-fiber MOPA producing micro-J pulses tunable in duration from 1-21 ps

This paper demonstrates a single polarisation, 1.06 µm Yb-doped fiber MOPA, delivering 21 ps pulses in a diffraction limited beam at repetition rates of up to 908 MHz and average output power of 100 W. The maximum pulse energy was 1.7 µJ at a repetition rate of 56 MHz, with corresponding peak power of 85 kW. The 100 W power was limited by available diode pump power and scaling to higher power levels is discussed. We also report self-phase-modulation based pulse compression which produced pulse durations as short as 1.1 ps from an external grating compressor. Using 4.2 ps pulses at a repetition rate of 227 MHz enabled 26 W of visible laser power (50% SHG efficiency) to be demonstrated