Concomitant production of protease and biosurfactant was optimized using agro-products, namely cornstarch and soy flour as carbon and nitrogen sources, respectively, by response surface methodology. An overall 2.3-fold increase for both protease (2954 U/ml) and biosurfactant (41 %) was achieved. Ultrafilteration using a 100 kDa membrane allowed a cost-effective purification of both protease and biosurfactant where the surfactant traps the protease on the membrane thereby detaining both in the retentate. These products were found to have a shelf life of I year in the dry form prepared by mixing sodium sulphate in the retentate. Thus, concomitant production of protease and surfactant, their easy formulation makes them attractive detergent additives. (c) 2005 Elsevier Ltd. All rights reserved.