Tamarind seed powder (TSP) was used as raw material for microbial production of citric acid. The maximum citric acid production was observed when the TSP-basal medium (TSP with inorganic nitrogen and phosphorus source) was supplemented with Mg2+, Fe2+, Cu2+ and Zn2+. The use of methanol and ferrocyanide as a modulator for citric acid production was studied. On methanol supplementation to the medium, ammonium nitrate was found to be better than ammonium carbonate as a source of inorganic nitrogen. Addition of ferrocyanide after sterilization to the medium containing methanol gave the maximum citrate production of 363 μg/ml.