Clavulanic acid (CA) produced by Streptomycesclavuligerus is degraded during the bacterial cultivation. Thephysical, chemical, and enzymatic effects, in order to understandthe degradation during the cultivation. The result showed that CAwas unstable in the production medium containing amoniumsalts and amino acids, owing to amonium ions and aminegroups. In addition, the degradation was not only due to instabilityof CA by metabolites and proteins, but also enzymes from S.clavuligerus such as β-lactamase and penicillin-binding proteins.However, the degradation caused by these enzymes was not highlysignificant compared with the degradation during the cultivation,