Monday, April 30, 2007

Piloting aerobic and anaerobic bioreactors for agitation scale-up

Gregory T. Benz, Benz Technology International, Inc., 2305 Clarksville Road, Clarksville, OH 45113

Most bioreactors are operated for the purpose of identifying optimum conditions for the biologic systems, such as temperature, nutrient composition, etc. Growth rate, yield or product distribution may be optimized in the pilot scale with little thought given on how to achieve similar results full scale when agitation influences results. In an aerobic process, the pilot conditions typically have more excess oxygen than full scale, more uniform DO distribution, higher agitator power/volume and lower superficial gas velocity than typical at production scale. In anaerobic processes, the mechanisms linking agitation to results have not been clearly identified, so empirical results should be studied at more than one scale to determine how to scale-up. This paper will give guidance on how to design appropriate experiments to measure scalable data for agitation for both kinds of processes, including how to address some intrinsic problems in such experiments.