A Quantitative Approach to Characterizing Cell Lysis Caused by Mechanical Agitation of Streptomyces clavuligerus

Streptomyces clavuligerusis a commercially important actinomycete that is used to produce clavulanic acid, a β‐lactamase inhibitor. Observations during 10 batch cultivations with S. clavuligeruson 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 increased to keep the dissolved oxygen level above 50% air saturation. A quantitative approach based on the calculation of elemental balances and a simple mathematical 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., μmax= 0.16 h−1and kd= 0.07 h−1, when the gassed power input increases above 1.1, 1.7, or 2.0 kW/m3, respectively, depending on the medium composition. The overall biomass yield on substrate is dramatically reduced in all experiments (>30%).