Suggestion 1: On day 2 we ran gels of the cell lysates from induced and uninduced e coli. It might be a good idea to load a sample of recombinant beta-gal on these gels to make it more clear where the induced beta-gal might be running on the gel.
Suggestion 2: On day 3 we purified beta-gal from our cell lysates and measured activity of the purified material. It might be fun for the students to measure activity of the supernatant as well. This would give them the opportunity to think about the efficiency of their purification and some steps that they might take to improve efficiency if it turns out their recovery was less than optimal.