Effects of copper on germination, growth and sporulation of Clostridium tyrobutyricum

The effects of copper (Cu(2+)) on spore germination, vegetative growth and sporulation of Clostridium tyrobutyricum, which is capable to causing texture and flavour defects in Emmental cheese, were studied. Spore suspensions of three different strains were used as starting material for two experimental set-ups. The first studied the effects of supplemented (0-30 ppm) copper in RCM medium during spore germination and vegetative growth of C. tyrobutyricum measured by plating. The second set-up studied the effects of copper (0-30 ppm) in RCM medium during growth and sporulation of C. tyrobutyricum as measured by optical density at 550 nm and by platings after heat treatment of the samples respectively. Inhibition of germination, vegetative growth and sporulation processes by copper was strain-dependent. Both sporulation and germination were more sensitive than vegetative growth of C. tyrobutyricum to the inhibitory effects of copper. Copper, at the concentrations investigated in this study, inhibits spore germination of C. tyrobutyricum strains. Consequently copper may reduce the risk of late blowing spoilage from in the germination of C. tyrobutyricum spores during the ripening period of Emmental cheese.