Biomedical subjects

Robert Puskeiler

Publications and source records attributed to Robert Puskeiler.

4 recordsLinked to original sources

PubMed2005

Methods and milliliter scale devices for high-throughput bioprocess design.

Based on electromagnetic simulations as well as on computational fluid dynamics simulations gas-inducing impellers and their magnetic inductive drive were optimized for stirred-tank reactors on a 10 ml-scale arranged in a bioreaction block with 48 bioreactors. High impeller speeds of up to 4,000 rpm were achieved at very small electrical power inputs (63 W with 48 bioreactors). The maxima of local energy dissipation in the reaction medium were estimated to be up to 50 W L(-1) at 2,800 rpm. Total power input and local energy dissipation are thus well comparable to standard stirred-tank bioreactors. A prototype fluorescence reader for 8 bioreactors with immobilized fluorometric sensor spots was applied for online measurement of dissolved oxygen concentration making use of the phase detection method. A self-optimizing scheduling software was developed for parallel control of 48 bioreactors with a liquid-handling system for automation of titration and sampling. It was shown on the examples of simple parallel batch cultivations of Escherichia coli with different media compositions that high cell densities of up to 16.5 g L(-1) dry cell mass can be achieved without pH-control within 5 h with a high parallel reproducibility (standard deviation<3.5%, n=48) due to the high oxygen transfer capability of the gas-inducing stirred-tank bioreactors.

Bioreactors↗

PubMed2005

Combined sulfite method for the measurement of the oxygen transfer coefficient k(L)a in bio-reactors.

The combined sulfite method is proposed for the measurement of oxygen transfer coefficients, k(L)a, in bio-reactors. The method consists of a steady-state and a dynamic measurement which are carried out under the same experimental conditions and thus yield data for both methods during one experiment. The applied experimental conditions are shown to avoid chemical enhancement during the steady-state measurement. Moreover, no parallel sulfite oxidation occurs during the oxygen saturation phase of the dynamic measurement. Under the applied experimental conditions, no information about the sulfite oxidation kinetics is required and possible metal ion impurities in sulfite salts do not influence the measurement. The characterization of a laboratory-scale bioreactor aerated with pure oxygen yields k(L)a values during the steady-state and the dynamic measurements that are in good agreement with the dynamic pressure method, the correctness of which is generally accepted. When air is used for absorption, the steady-state measurement yields k(L)a values that correlate to the correct variant of the standard dynamic method. The dynamic measurement with air absorption yields a k(L)a value which considers the influence of the non-uniform bubble size distribution present in bubble-aerated bio-reactors.

Bioreactors↗

PubMed2005

Reconstitution of the peridinin-chlorophyll a protein (PCP): evidence for functional flexibility in chlorophyll binding.

The coding regions for the N-domain, and full length peridinin-chlorophyll a apoprotein (full length PCP), were expressed in Escherichia coli. The apoproteins formed inclusion bodies from which the peptides could be released by hot buffer. Both the above constructs were reconstituted by addition of a total pigment extract from native PCP. After purification by ion exchange chromatography, the absorbance, fluorescence excitation and CD spectra resembled those of the native PCP. Energy transfer from peridinin to Chl a was restored and a specific fluorescence activity calculated which was approximately 86% of that of native PCP. Size exclusion analysis and CD spectra showed that the N-domain PCP dimerized on reconstitution. Chl a could be replaced by Chl b, 3-acetyl Chl a, Chl d and Bchl using the N-domain apo protein. The specific fluorescence activity was the same for constructs with Chl a, 3-acetyl Chl a, and Chl d but significantly reduced for those made with Chl b. Reconstitutions with mixtures of chlorophylls were also made with eg Chl b and Chl d and energy transfer from the higher energy Qy band to the lower was demonstrated.

Carotenoids↗

PubMed2005

Miniature bioreactors for automated high-throughput bioprocess design (HTBD): reproducibility of parallel fed-batch cultivations with Escherichia coli.

To verify the reproducibility of cultivations of Escherichia coli in novel millilitre-scale bioreactors, fully automated fed-batch cultivation was performed in seven parallel-operated ml-scale bioreactors with an initial volume of 10 ml/reactor. The process was automatically controlled by a liquid-handling system responsible for glucose feeding, titration and sampling. Atline analysis (carried out externally of the reaction vessel with a short time delay) comprised automated pH and attenuance measurements. The partial pressure of oxygen (pO2) was measured online by a novel fluorimetric sensor block measuring the fluorescence lifetime of fluorophors immobilized inside the millilitre-scale bioreactors. Within a process time of 14.6 h, the parallel cultivation yielded a dry cell weight of 36.9+/-0.9 g.l(-1). Atline pH measurements were characterized by an S.D. of <1.1% throughout the process. Computational-fluid-dynamics simulation of single-phase flow yields a mean power input of 21.9 W.l(-1) at an impeller speed of 2800 rev./min corresponding to a power number (NP) of 3.7.

Automation↗