I found an old paper by ML Cohn stating that Casein hydrolysate improves the recovery of some fastidious Mtb strains. I am doing a project with MGITs but it involves removing some of the 7H9 medium with Casein peptone. I was wondering if Casein peptone is essentially the same as Casein hydrolysate and whether this could reduce the recovery / growth of some Mtb strains. Many thanks
Chemically, the composition of casein peptone and casein hydrolysate will be rather similar. The peptone version is classically defined as casein digested with pepsin, a fairly non-specific protease. So this is an enzymatic digestion (tryptone is related, but uses instead trypsin, a more specific protease so the peptide fragments in the medium are on average longer). The hydrolysate is a partial chemical hydrolysis of the casein protein. It can be done at elevated temperatures, or under acidic or basic conditions (and then neutralized after the reaction). It's possible Mtb could prefer one over the other, but this I am unsure about.
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