Using Corn Husk Powder as a Novel Substrate to Produce a Surface Active Compound from Labrenzia aggregate KP-5

In this study, surface active compound (SAC)-producing bacterial isolates were evaluated for SAC production using corn husk powder (CHP) as a sole carbon source. From the 51 isolates screened, Labrenzia aggregate KP-5 produced the highest SAC activity. The highest SAC production (3.51gL(-1)) was obtained when the strain was cultivated in a minimal salt medium containing 40gL(-1) CHP and 1gL(-1) commercial monosodium glutamate at 30 degrees C and 150rpm after 51h of cultivation. The produced SAC had the ability to decrease the surface tension of water from 72.0 to 25.5mNm(-1), with the critical micelle concentration of 9mgL(-1) (11.07mM) and exhibited the highest emulsification activity (EA) of 81% against motor oil. The SAC showed stability at 4-121 degrees C and pH 4-10 against the surface and EA of vegetable oils and hydrocarbons, and showed tolerance at high salt concentrations (1-10% NaCl). The chemical structure of the SAC was confirmed as a rhamnolipid using Fourier transform infrared spectroscopy, nuclear magnetic resonance spectroscopy, and mass spectrometric analysis. The SAC did not exhibit inhibitory effects on various vegetables tested; however, strong inhibitory activity against Gram-positive and Gram-negative bacteria was observed. The application of SAC for microbial enhanced oil recovery by sand saturated with used lubricating oil resulted in above 89% of oil removal. The properties of the SAC we obtained from CHP have potential applications especially for microbial enhanced oil recovery and/or reducing the intensity of environmental contamination. In addition, the obtained SAC is a suitable alternative to antimicrobial agents.