A quantitative approach to characterizing cell lysis caused by mechanical agitation of Streptomyces clavuligerus

Streptomyces clavuligerus is a commercially important actinomycete that is used to produce clavulanic acid, a beta -lactamase inhibitor. Observations during 10 batch cultivations with S. clavuligerus on defined media have led to the finding that the organism is very sensitive to shear when grown in batch cultures with increasing stirrer speed. The stirrer speed was increas ed to keep the dissolved oxygen level above 50% air saturation. A quantitat ive approach based on the calculation of elemental balances and a simple ma thematical model is proposed to characterize the biomass lysis. Finally, a linear relation between biomass yield and observed specific growth rate is determined, Results show that cell lysis occurs at a high degradation rate, e.g., mu (max) = 0.16 h(-1) and k(d) = 0.07 h(-1), when the gassed power i nput increases above 1.1, 1.7, or 2.0 kW/m(3), respectively, depending on t he medium composition. The overall biomass yield on substrate is dramatical ly reduced in all experiments (>30%).