The morphology of filamentous fungi.

The morphology of fungi has received attention from both pure and applied scientists. The subject is complicated, because many genes and physiological mechanisms are involved in the development of a particular morphological type: its morphogenesis. The contribution from pure physiologists is growing steadily as more and more details of the transport processes and the kinetics involved in the morphogenesis become known.

A particulate pulse-release system and mathematical description with the Maxwell-Stefan theory.

In this contribution both the development of a multi-particulate delayed release system with release properties dependent on the swelling of an UV crosslinked coating and a mathematical model to describe its release properties are presented. The formulation consists of a water-soluble core coated with a copolymer of methacrylic acid and ethyl acrylate. Incorporating a network of crosslinked pentaerythritol triacrylate decreases the water-solubility of the coating.

Fluid bed agglomeration with a narrow droplet size distribution.

In the fluid bed agglomeration processes liquid distribution influences the agglomerate growth. We developed a new nozzle that produces uniform droplets, which allows droplets to be easily controlled in size independently of liquid- and airflow of the nozzle. It was found that the spray rate and the mixing in the spray zone determine the average granule size and that there is linear relation between the number of droplets of which a granule consists and its volume, at the early stage of the process.

Microdialysis of glucose in subcutaneous adipose tissue up to 3 weeks in healthy volunteers.

Objective: To measure possible changes in dialysate glucose concentrations over time, to validate the diffusional model for glucose transport from tissue to the probe, and to evaluate the actual glucose concentration in adipose tissue.

Research Design And Methods: Glucose concentrations in the subcutaneous adipose tissue of five healthy subjects (age 25 +/- 2.7 years, BMI 23.

Experimental simulation of oxygen profiles and their influence on baker's yeast production: II. Two-fermentor system.

A reactor configuration consisting of two reactors with an exchange flow was used for the experimental simulation of large-scale conditions. The influence of fluctuations in oxygen concentration on the growth and metabolite production of baker's yeast was investigated by sparging one fermentor with air and one with nitrogen gas. It was found that the biomass yield decreased and the metabolite formation increased with rising circulation time (longer oxygen-unlimited and oxygen-limited periods).

Experimental simulation of oxygen profiles and their influence on baker's yeast production: I. One-fermentor system.

In production-scale bioreactors microorganisms are exposed to a continually changing environment. This may cause loss of viability, reduction of the yield of biomass or desired metabolites, and an increase in the formation of by-products. In fed-batch production of baker's yeast, profiles may occur in substrate and oxygen concentrations and in pH.

An integral dynamic model for the UASB reactor.

In this article a dynamic model of a continuous working UASB reactor is described. It results from the integration of the fluid flow pattern in the reactor, the kinetic behavior of the bacteria (where inhibition and limitation were taken into account), and the mass transport phenomena between different compartments and different phases. The mathematical equations underlying the model and describing the important mechanisms were programmed and prepared for computations and simulations by computer.

Modeling the liquid flow in up-flow anaerobic sludge blanket reactors.

By means of stimulus-response experiments an Li(+) tracer, models for the fluid flow in a 30-m(3) UASB reactor, used for the anaerobic treatment of wastewater, were tested. From the model with the best fit it could be derived that both the sludge bed and the sludge blanket can be described as perfectly mixed tank reactors with short-circuiting flows; the settler volume acts like a plug-flow region.Apart from the volumes of the different flow regions, two parameters are necessary and sufficient to describe the fluid flow in a well functioning UASB reactor, i.

Kinetics of anaerobic purification of industrial wastewater.

As a part of the development of an integral mathematical model describing the up-flow anaerobic sludge blanket (UASB) reactor, the kinetics of the conversion of organic wastes has to be known. We compared the Monod model with the model proposed by Andrews et al. Together with the assumption that the substrate for the anaerobic bacteria is formed by nonionized, volatile fatty acids, the Andrews model is able to describe substrate inhibition and reactor failure due to pH changes.

Scale-down and optimization studies of the gluconic acid fermentation by Gluconobacter oxydans.

To simulate production-scale conditions of gluconic acid fermentation by Gluconobacter oxydans, different experimental setups are presented in this study. From the determination of the time constants of a production-scale reactor, it can be concluded that mixing and oxygen transfer are the rate-limiting mechanisms. This results in oxygen concentration gradients which were simulated in a one-compartment reactor in which the oxygen concentration was fluctuated by a fluctuated gassing with air and nitrogen.

Theory and applications of unstructured growth models: Kinetic and energetic aspects.

Microbial kinetics and energetics are discussed in connection with the formulation of unstructured growth models. The development of microbial energetics and the use of macroscopic methods in the study of microbial growth are briefly evaluated. The general approach to the modelling of microbial growth has been critically discussed and a strategy for the formulation of unstructured models is presented.

Continuos IBE fermentation by immobilized growing Clostridium beijerinckii cells in a stirred-tank fermentor.

The potential of continuous isopropanol-butanol-ethanol (IBE) fermentation by Ca-alginate-immobilized Clostridium beijerinckii cells in a continuous stirred-tank reactor is investigated. A mathematical model is presented to describe steady-state reactor performance. It appeared to be possible to use the biocatalyst particles repeatedly for successive fermentations (at least three times for a total duration of two months).

Modeling of bacterial growth; formulation and evaluation of a structured model.

Models which consider changes in the composition of biomass in response to environmental changes are called Structured models. They provide a more comprehensive description of microbial behavior than unstructured models. Compared with the unstructured modeling efforts, very little has so far been done on the theory and practice of structured model building.

Unstructured model for growth of mycelial pellets in submerged cultures.

An unstructured model is presented to describe growth of mycelial pellets in submerged cultures. This model integrates growth kinetics at the scale of the hyphae with the physical mechanisms of mass-transfer processes at the scale of the pellets and the fermentor. The main elements of the model are biomass, substrate, and oxygen balances for the liquid phase and the pellets.