[en] Metallothioneins (MTs) are cystine rich proteins found in all living organisms and play important roles as a radical scavenger and in metal homeostasis. Their optimum culture conditions and media composition of B. pantothenticuszn and B.pantothenticuscu were 1.5 g/L maltose and 1.5 g/l lactose as media carbon sources respectively, 48 hrs incubation period, 35 degree C, ph 8, 200 r.p.m. agitation speed, 26 g/L ammonium dihydrogen orthophosphate as nitrogen source, 0.5 g/L cysteine, 6% of 2.5x107 c.f.u./ml. inoculum size and exposure to a level dose of 4 kGy of gamma radiation. All the previous parameters increased the production of MT by B. pantothenticuszn and B.pantothenticuscu strains 12 and 10 times, respectively compared to the parent strains