Hydrodynamics and mixing in a multiple air-lift loop reactor

A new bioreactor, in which a series of air-lift reactors with an internal loop is incorporated into one vessel, is introduced. With this multiple air-lift loop reactor (MAL) and approximation of an aerated plug-flow fermentor is strived for. Mixing, liquid velocity, and gas hold-up were measured as a function of the gas flow rate in this new internal-loop reactor geometry. As a reference, hydrodynamics were also investigated in a conventional internal-loop reactor. A model description of the hydrodynamics in the second compartment of the MAL is given. This model is based on a two-phase, drift-flux model and a friction coefficient. Frictional losses were independent of the reactor bottom geometry, and were observed to increase with the gas flow rate as a result of the presence of stationary gas bubbles in the downcomer. The hydrodynamics and mixing of the second MAL compartment were comparable with those of conventional internal-loop reactors.

Sucrose conversion by immobilized invertase in a multiple air-lift loop bioreactor

A new bioreactor series within one vessel, the multiple air-lift loop reactor (MAL), is introduced. In the MAL, a series of air-lift loop reactors is incorporated into one vessel. From residence time distribution studies, it was shown that the three-compartment MAL behaves as a series of three ideal mixers. A continuously operated MAL, containing immobilized invertase as a model biocatalyst, was evaluated. The advantage of approaching plug flow by using a bioreactor cascade could be shown by comparing substrate conversion in the three-compartment MAL to that in a single vessel at the same overall dilution rate. This was done for two sets of experimental conditions, which were chosen by using a previously developed model. Intrinsic kinetic parameters of the immobilized enzyme, needed for the model calculations, were determined experimentally. Model calculations gave good approximations of the results. The model incorporates external mass-transfer resistance and diffusion and reaction in the biocatalyst beads.

Application of a Nociceptive Test Battery to Assess Potential Synergy between Two Analgesics in Healthy Subjects

Chronic pain management remains a major challenge due to the risks associated with conventional treatments, such as opioids and NSAIDs, which carry significant risks, including addiction, tolerance, and adverse side effects, particularly with prolonged use. Combining opioid with nonopioid drugs offer a potential solution, as it may minimize opioid-related side effects by reducing the required opioid dose. We performed a study to compare the analgesic effects and safety of a pregabalin-morphine combination to each drug alone and placebo in healthy volunteers. A randomized, double-blind, placebo-controlled crossover design was used, with subjects receiving 300 mg of pregabalin combined with 3 and 7 mg of morphine, morphine only, pregabalin only, or a double placebo. Analgesic effects and CNS side effects were assessed up to 10 h postdose using nociceptive and neurocognitive test batteries. Results demonstrated that the pregabalin-morphine combination significantly increased pain tolerance compared to either drug alone on several pain tests (cold pressor, electrical burst, electrical stair, and pressure pain) with only minimal additional CNS side effects compared to monotherapy and placebo. This study indicates that validated nociceptive and CNS test batteries were suitable to assess the potential of opioid-sparing combination therapies in an experimental setting.