1. Can we freeze microbial cultures at normal freezing temperature?
  2. How long we can keep reference prepared cultures?
  3. How much sub-cultures can be done from 4 passage cultures.
    It is normally recomended that you sub-sulture weekly upto one month and then dicard your culture. if it is the case then it become quite expensive.
  4. What will be the duration of sub-culturing one week, 15 days or one month. is there any reference?
  1. You can stored at -80 deg C in glycerol.
  2. usually 2 months in slant but it is depends on how frequent u use it.
  3. 2

subculturing in one month is recommended, but some organisms requires one week subculturing. it depends upon the nature of organism

Dear Mr. Zahid,
U please refer Page No. 80 of USP 30 and u will get all the answers.