Dear Kimverly,

Yes, solid state culture is one way to produce citric acid by solid state fermentation. This has been done in one company in Lampung (South Sumatra), Indonesia. Briefly speaking, a mold that can produce citric acid is grown within the solid medium and harvested after about two weeks. It is then extracted by using warm water, then the solid waste is disposed, while the citric acid is separated or extracted from the liquid phase, followed by purification process.