An experimental study was carried out to examine the effects of different macro-mineral elements on growth and l-glutamic acid fermentation by a mutant Micrococcus glutamicus AB100. It was required for improved production of l-glutamic acid by this mutant. K2HPO4, 0.15%; MgSO4.7H2O, 0.03% and CaCO3, 0.04% were required for improved production of l-glutamic acid by this mutant. KH2PO4, NaH2PO4.H2O, HCl, NaCl and CaCl2 showed no effect on growth and l-glutamic acid accumulation, where as K2B4O7.X H2O showed negative impact on growth and the production. L-glutamic acid production was increased significantly (p<0.01) from 14.8 mg/ml to 18.8 mg/ml and dry cell weight was increased significantly (p<0.01) from 7.3 mg/ml to 9.8 mg/ml after addition of the necessary macro-mineral elements in the fermentation broth.