Abstract: By adopting blood-agar procedure combined with surface tension screening strategy, an efficient surfactant-producing bacterial strain DY-9 was successfully isolated from the produced water from low-permeability Gaotaizi oil reservoir, Daqing Oilfield of Northeast China. The comparison with the homoeologous 16S rDNA sequences deposited in the GenBank showed that the DY9 had a 99% sequence similarity with Bacillus licheniformis. When cultured on a medium with 20 g·L^-1 of molasses as the sole carbon source at 180 r·min^-1 and 45 °C, the DY-9 could grow well, and decrease the surface tension of culture broth from initial 69.3 mN·m^-1 to 26.5 mN·m^-1 within 24 h. After cultured for 48 h, the maximum raw biosurfactant yield of the strain reached 0.48 g·L^-1, and the critical micelle concentration was 28 mg·L^-1. The biosurfactant produced by the DY9 could keep stable under the conditions of high temperature (120 °C) for 1 h, high salinity (12% NaCl), and wide pH (2-12), and the surface tension of the zymotic fluid within 48h was lower than 30 mN·m^-1. The analysis with infrared spectroscopy (IF-TR) and high-pressure liquid chromatographymass spectrometry (HPLC-MS) revealed that the surface-active product of the DY-9 was a cyclic structure lipopeptide biosurfactant.

Key words: tobacco, latently fragrant substance, stability, genotype and environment interaction, AMMI model.