What is the appropriate statistical test to use when comparing yield of a protein from a bacteria at different pH?

The yield at a step in the procedure is the amount of target (either total target protein or total activity) at that step divided by the amount of target in the first step (defined as 100%).

The various protein expression systems are bacteria, yeast, insect or mammalian systems. The following factors determine the type of expression system used to produce recombinant proteins: time spent in expressing the protein. ease of handling the expression system.

by using gram negative bacterium eschericia coli (E.coli)