No abstract

The interest in cellulose produced by bacteria from surface cultures has increased steadily in recent years because of its potential for use in medicine and cosmetics. Unfortunately, the low yield of the production process has limited the commercial usefulness of bacterial cellulose. This series of three papers dealing with the production of bacterial cellulose using (batch) surface culture, firstly present a complete and complex analysis of the overall system, which allows a fundamental optimization of the production process to be performed. This material has many applications but the low yield of the process limits its commercial usefulness. In part 1, the effect of the rate of mass transfer of substrate on the microbial process, which is characterized by the growth of the bacteria, product formation, and the utilization of the substrate by the bacteria, is studied. A fundamental model for the diffusion of glucose through the growing cellulose layer is proposed and solved. The model confirmed that the increase in diffusional resistance is indeed significant but other factors will also need to be taken into account.

No abstract

Parts 1 and 2 have shown that the rate of production of bacterial cellulose stagnates because of the limitation of substrate supply and a wall effect, which hinders the removal of the product from the active cell zone. This paper demonstrates, how both of these problems can be eliminated in a novel bioreactor, where the substrates (mainly glucose and oxygen) are both fed directly to the surface of the product cellulose. This involves the generation of an aerosol spray of glucose and its even distribution to the living bacteria on the medium‐air interface. The apparatus was built and operated up to eight weeks with a constant rate of cellulose production. The aerosol system provides the basis for an economic production of bacterial cellulose in surface culture.

The common way for the production of bacterial cellulose in surface culture is to use culture boxes or beakers with vertical walls, where the maximum achievable thickness is around 4 cm. In order to improve this, it is necessary to study factors limiting the production. In part 1, the mass transfer influences of the substrate have been investigated. Now we look at a “wall effect”. It is noted that the growing cellulose is in contact with the wall of the box or beaker, and moves downwards into the nutrient broth as time proceeds. Experiments have been carried out where this wall contact was eliminated and a constant rate of production over several weeks was found. This indicates the importance of understanding the role of the wall in the usual surface culture.