Richard Mormino

Composites of bacterial cellulose and paper made with a rotating disk bioreactor

Suspended solids in the nutrient medium for Acetobacter xylinium in a rotating disk bioreactor become incorporated into the gelatinous mat of bacterial cellulose as it forms. Embedding fibers of ordinary cellulose creates composites with enhanced strength and the toughness of bacterial cellulose. Purified cellulose and elongated fibers from paper are incorporated differently than are spherical particles such as silica gel. About 90% of the final cellulose can come from scrap paper, and dried composite sheets were much stronger than plain bacterial cellulose per unit area.

Auxostats for continuous culture research

Abstract A device that uses the rate of feeding to control a state variable in continuous culture is termed an auxostat. The organisms establish their own dilution rate. While the well-known chemostat is stable and simple for investigating continuous cultivation at low to moderate dilution rates, an auxostat tends to be much more stable at high dilution rates. Population selection pressures in an auxostat lead to cultures that grow rapidly. Practical applications include high-rate propagation, destruction of wastes with control at a concentration for maximum rate, open culturing because potential contaminating organisms cannot adapt before washing out, and operation of processes that benefit from careful balance of the ratios of nutrient concentrations.

Environmental implications of microbial cellulose

Abstract The strong, tough, highly pure cellulose synthesized by microorganisms is just emerging as a new industrial product with exciting new applications in medicine, in foods, and in paper and packaging as well as potential for use in industrial separations. Making a polymer by bioprocessing is inherently much less damaging to the environment than are petrochemical processes, and this cellulose may substitute for plastics and for special grades of paper. This would eliminate some petrochemical processing and the highly pollutional steps for pulping and bleaching of wood cellulose. Wastes that contain cellulose can be converted to sugars that are substrates for the microorganisms that make cellulose. Microbial cellulose produced rapidly by Acetobacter xylinium in a rotating disk reactor is a gel with 100 to 200 parts of water per part of cellulose. Much of the water can be removed mechanically so that little drying is needed to get a product resembling parchment in its appearance and properties. Small amounts of microbial cellulose added to paper greatly improve its strength. This new cellulose may compete well with existing polymers and paper on its own merits, and environmental benefits may make the cost comparisons even more favorable.