A removable membrane, or cover, for a disposable food container includes a membrane portion at least partially defined by a circular outer perimeter edge. The polynucleotides of the invention can be used to construct genetically modified microorganisms blocked in 3-ketosteroid 9\u03b1-hydroxylase activity, which are useful in the microbial degradation of steroids to accumulate certain steroid products. The transfer of data is then controlled based on the characteristic which has been identified.