Blood clot degrading enzymes are very much useful in combating cardiovascular diseases. An organism primarily isolated from soil, identified as Bacillus cereus NK1 was found to secrete an extracellular protease and the enzyme was identified to degrade fibrin. Response surface methodology was applied to optimize the URAK production medium by B. cereus NK1. The optimized medium obtained from central composite rotary design (CCRD) composed of glucose: 0.5%; soybean meal: 0.5%: calcium chloride: 0.5% and MgSO4: 0.2%. The production of URAK by the optimized medium was 6326.98 FU/ml. Initial experiments showed that the maximum production of URAK occurred at 12th h at pH 9. The efficacy of the medium was further studied in a fermentor as batch fermentation with the same medium optimized by RSM and the yield was comparable with that of the shake flask culture. The maximum activity obtained from fermentor was 6266.66 FU/ml, at the 12th h. PHB was synthesized by B. cereus DV-4 and used for the synthesis of PHB nanoparticles. URAK was purified by ion exchange chromatography and immobilized on PHB nanoparticles. (C) 2010 Elsevier Inc. All rights reserved.