I am planning to use the MgCO3 as a CO2 source for bacterial growth in the media, due to its lower solubility with water I am unable to use it directly, may I get any valuable suggestions, please.
As others have suggested, you can increase the solubility of the MgCO3 by adding an acid. If you use a weak organic acid that will also increase the CO2 and HCO3- content of your solution. But any increase in CO2(aq) above atmospheric pressure will be out-gassed to the atmosphere unless you are using a sealed container.