Inclusion of solid particles in bacterial cellulose.

Depending upon the strain and the method of cultivation, bacterial cellulose can be reticulated filaments, pellets, or a dense, tough gel called a pellicle. The pellicular form is commonly made by surface culture, but a rotating disk bioreactor is more efficient and reduces the time of a run to about 3.5 days instead of the usual 12-20 days. Particles added to the medium as the gel is forming are trapped to form a new class of composite materials. Particles enter the films that are forming on the disks at rates depending on the size and geometry of the particle, as well as the rotational speed and concentration of the suspension.

Protein fractionation using fast flow immobilized metal chelate affinity membranes.

A new group-specific affinity membrane using metal chelates as ligands and inorganic glass hollow fiber microfiltration membranes as support matrices is developed and tested. The study focused on developing the optimum activation and coupling procedures to bind the chelating agent (iminodiacetic acid, IDA) to the surface of the microporous glass hollow fiber membrane and testing the resultant affinity membrane. Starting with three different glass surfaces, five modification reactions were evaluated. All the modified "active surfaces" were first tested for their protein adsorptive properties in batch mode with suspended microporous glass grains using model proteins with known binding characteristics with Cu-IDA systems. The metal loading capacities of the surfaces exhibiting favorable fractionation were then measured by atomic absorption spectroscopy.The results were compared with the results obtained with a commercial material used in immobilized metal affinity column chromatography. The protein binding characteristics of the hollow fiber affinity membranes were also evaluated under conditions of convective flow. This was performed by flowing single solute protein solutions through the microporous membrane at different flow rates. These results were then used to estimate the optimum loading and elution times for the process. A mathematical model incorporating radial diffusion was solved using a finite difference discretization method. Comparison between model predictions and experimental results was performed for four different proteins at one flow rate. These results suggested that the kinetics of adsorption was concentration dependent. Finally, the hollow fiber affinity membranes were challenged with two component mixtures to test their ability to fractionate mixed protein solutions. Efficient separation and good purity were obtained.The results presented here represent the development of a new fast flow affinity membrane process-immobilized metal affinity membranes (IMAM). (c) 1994 John Wiley & Sons, Inc.