Bacillus circulans, a heterotrophic microorgansim has been used for the recovery of copper, nickel and cobalt from sea nodules. The organism was revived in nutrient medium and adapted gradually on sea nodules prior to leaching. Bioleaching studies were carried out in shake flasks containing sea nodule powder with growth medium and adapted microbial culture under a range of conditions such as pH, pulp density, particle size of nodules and temperat-ure. Metal recovery was highest in 30 days but the rate of recovery was slow after 25 days of bioleaching. A 92% Cu,
73% Ni, 72% Co, 38% Mn and 17% Fe was recovered at pH 2 in 25 days at 35°C temperature. XRD identification of residue showed the presence of some lower and mixed oxidation phases of manganese and some unaltered iron phases. The biodissolution of metals was direct enzyme leading to reduction of Mn (IV) to Mn (II) and Fe (III) to Fe (II)
