In the present investigation different strains which showed the accumulation of PHB in the nitrogen deficient medium were isolated from sediment samples collected from Vellar estuary (Lat 11 o 29'24"N and Long. 79 o 45' 36" E). Among these Vibrio mimicus which showed the maximum PHB accumulation was selected for further study. The optimum growth conditions of V. mimicus were 36 hrs of incubation period, 35C, pH-8, 1% NaCl, 4% glucose and 0.03% yeast extract. Mass scale was done by keeping the above ideal parameters; which resulted in 18.6g/L of PHB production on dry weight basis.