Question

What would happen when you grow a recombinant in a bioreactor but forget to add antibiotic to the medium in which the recombinant is growing.

Answer 1

In the absence of antibiotic, there will be no pressure on recombinants to retain the plasmid (containing the gene of your interest). Since, maintaining a high copy number of plasmids is a metabolic burden to the microbial cells, will thus tend to lose the plasmid.