Correlating beta-lactamase expression to absorbance > When penicillin-resistant bacteria are grown in liquid culture media, β-lactamase is secreted into the medium. The supernatant of such a medium can be assayed for β-lactamase activity. Culture supernatants different organisms , which are suspected to be penicillin-resistant, were obtained and were assayed for β-lactamase activity. The corresponding absorbance value were measured at a certain wavelength. Let us assume that supernatant from organism 1's culture had absorbance value X and 2 had absorbance value Y. My question : If X>Y, does that mean that more β-lactamase was being produced by organism 1 ?

In the β-lactamase test, an inhibitor of β-lactamase is added to a sample of the culture medium. The inhibitor binds to the enzyme and changes its color, which is in direct correlation to the concentration of the β-lactamase. More β-lactamase means more inhibitor binding and this results in more color development leading to a higher absorption. So higher absorption means more β-lactamase in the supernatant.