I am wondering why the incubation time for probiotic cells to grow in milk is shorter than in MRS broth. According to the protocol, the bacteria strains need to culture in MRSB for 3 days before transfer to milk. Why do we need 3 days in MRSB but only 1 day in milk?
In actual practice, you can only approximate the time to: a day in milk or 3 days in MRS. It might vary from strain to strain. however I guess availability and substrate utilization in solid agar requires performance of more metabolic pathways by the strain, than compared to in liquid media (milk). Moreover, Agar is indigestible for many organisms. This might be a possible explanation.
Have a great day.
Milk has less nutrition than MRS, so you have to start with very good inoculation starter with big CFU value to inoculate the milk. However, you have to keep in mind that MRS contains glucose as a carbon source while milk has mostly lactose. you have to determine with what carbon source your strain grows better then investigate growth time accordingly.
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