Two prototype 24-unit microbioreactors are presented and reviewed for their relative merits. The first used a standard 24-well plate as the template, while the second consisted of 24-discrete units. Both systems used non-invasive optical sensors to monitor pH and dissolved oxygen. The systems were used to cultivate Escherichia coli. Both designs had their merits and the results obtained are presented. In addition, dissolved oxygen control was demonstrated at the milliliter scale and 24 simultaneously monitored fermentations were successfully carried out. These results demonstrated high quality high throughput bioprocessing and provide important insights into operational parameters at small scale. ß 2005 Wiley Periodicals, Inc.

We employ fully atomistic molecular modeling to investigate the concentration dependence of the electrooptic coefficient of two guest-host polymer composites. Using classical molecular dynamics, we record the time-evolution of the guest-host system under the application of an external electric field. Through analysis of the orientation of the nonlinear optical chromophores in the guest-host composite with respect to the direction of the external electric field, we calculate the orientational parameter N < cos 3 θ >, with N being the number density of chromophores in the composite. This parameter is directly proportional to the electrooptic coefficient. We find agreement between the concentration dependence of the electro-optic coefficient calculated through our simulation and that from experimental data and also from Monte Carlo models.

A novel optical sensor was used to study mixing and mean circulation time in a model minibioreactor (12.5 mL stirred vessel, equipped with a paddle impeller). Rotational rates in the range of 10-1,000 rpm corresponding to Reynolds number between 14 and 1,350 were studied. Results suggest that depending on the impeller rotational speed, mixing times up to 214 +/- 87 s can be reproducibly achieved. The minibioreactor was operated in the transitional regime, and it was determined that the non-dimensional form for mixing time, NTheta(M) was linearly dependent on Reynolds number. A linear correlation between mean circulation time and the inverse of rotational speed was also determined. The mean circulation time dependence on rotational speed in the 12.5 mL stirred vessel is similar to those found in large-scale stirred vessels. These results suggest that mixing and circulation times found in large-scale reactors can be replicated in minibioreactors.

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