Cell growth conditions for preparing electrocompetent cells
I'm new so I can't make this a comment, and I don't think the other commenter addressed your questions so here it goes: I don't think there will be much difference, if any, between 0.2 and 0.3 OD. Once you get higher and the cells start transitioning into a stationary phase is a different story. Did you mean to ask about 0.03 OD as well (you wrote 03.)? I'm not an expert in E. Coli, but they would probably be less likely to produce proteins that are contact inhibited. Sub-optimal temperatures may have a minor effect on growth, but I don't believe this will initiate much change or induce production of large amounts of cold shock proteins.