OXYGEN-TRANSFER DEFICIENCIES IN STARCH-BASED MEDIA

Insufficient oxygen transfer in a highly viscous media with varying viscosity occurs during the degradation of starch by Bacillus licheniformis. Oxygen transfer rate (OTR) decreased below 0.3 g l-1 h-1 for viscosities above 5 to 10 mPa.s and agitation speeds lower than 710 rev/min. Increasing agitation speeds by 30 to 50% compensated for the decrease in OTR for viscosities between 10 and 200 mPa.s. A dual impeller is considered essential for growth improvement.