We are considering trying to add additives to bacterial cultures to see if they improve solubility of some proteins we express: L-arginine, glycyl-glycine, sorbitol and betaine. I would be glad to receive recommendations and experiences, also if they haven't worked.
Side-question: should we get cell culture-certified compounds, or would "normal", much more economical ones suffice? (i.e. are they likely to contain side-products that would affect bacterial growth?).