A kind of melanin was synthesized from L tyrosine by the tyrosinase producing immobilized bacteria（P.maltophilia 135）. The ultraviolet visible absorption spectrum of the melanin showed a steadily increasing absorption ranging from 600 nm to 210 nm with a peak at about 210 nm. In the infra red spectrum of the melanin

there were characteristic absorption at about 3 μm and 6 μm. The above results verified that the product we had got was indeed a kind of melanin. The shake culture results showed a temperature optimum of 30 degree C and a pH optimum of 9.5. Traces of cupric ions

plenty of oxygen supply and less L tyrosine addition were favorable for melanin synthesis.The immobilized cells shaken in the physiological saline exhibited higher operational stabilities

in which the immobilized cells can be used 9 times repeatedly with 180 hours.