subsequently, a nonsterile organic medium containing some vitamins (glycine(c2h5no2),nicotinic acid (c6h5no2), pyridoxine hydrochloride (c8h12cino3) and thiamine hydrochloride (c12h18c12n4os)) was passed through a prepared mf membrane (sterilized at the temperature 121 c for 20 min) down to the bottle containing the mineral medium