The strain used in this work was R. erythropolis ATCC 25544 which was routinely maintained in the laboratory by periodic subculturing in GMP medium [20] consisting of 0.1 g/l glucose, 0.02 g/l yeast extract, 0.04 g/l peptone, 0.04 g/l meat extract, 0.05 g/l NaCl, 0.0025 g/l MgSO4 and 0.25 g/l agar.