Reclamation of squid pen by Bacillus licheniformis TKU004 for the production of thermally stable and antimicrobial biosurfactant

Bacillus licheniformis TKU004 produced biosurfactants in a medium with 1% squid pen powder as the sole carbon/nitrogen source at 37 1C for 1 day by using a baffled base flask, showing a growth-associated production. The biosurfactant was extracted from the culture supernatant by acid precipitation, extraction of ethyl acetate and methanol with the yield of 0.55 g/L. The biosurfactant could reduce surface tension of water from 72.30 to 25.42 mN/m at a concentration of 350 mg/L and the emulsification index of machine oil reached 68% after 24 h. The biosurfactant showed stability including thermal (121 degrees C, 20min) and pH (7-11) stability regarding the surface tension reduction and the emulsification capacity of machine oil, and tolerance under salt concentrations (<2%). The biosurfactant also showed antimicrobial activity significantly against cell growth of E. coli BCRC13086 and S. aureus BCRC10780. The results obtained in this work are noteworthy for possible biosurfactant production from SPP with potential of application in removal of oil and in the future to gasoline-contaminated ocean shores for ecological protection purposes. Besides, it is also possible to be applied as a biocontrol agent. (C) 2011 Elsevier Ltd. All rights reserved.