A highly efficient demulsifying strain, LH-6, was isolated from petroleum-contaminated soil and identified as Bacillus cereus by 16S rDNA gene analysis. It achieved 95.61 and 95.40 % demulsifying ratios within 12 h for water-in-oil (W/O) and oil-in-water (O/W) model emulsions, respectively. Fourier transform infrared spectroscopy (FT-IR) and thin-layer chromatography (TLC) detections indicated that the LH-6's extracellular biodemulsifiers were different types of lipopeptides for the W/O and O/W emulsions. Optimization of the culture medium composition was conducted to improve the biosynthesis and demulsifying efficiency of the biodemulsifier. The optimal carbon source was liquid paraffin, while waste frying oil could also be an alternative carbon source. The optimal nitrogen sources were ammonium sulfate and yeast extract. To further enhance the biodemulsifier efficiency, the optimal cultivation conditions were determined using response surface methodology (RSM) based on central composite rotation design (CCRD). Using the optimized cultivation conditions, the demulsifying ratios increased to 98.23 and 97.65 % for the W/O and O/W model emulsions, respectively.

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A Gram-stain-positive, facultatively anaerobic, endospore-forming, irregular rod-shaped bacterium, designated DB13260 T , was isolated from tropical rainforest soil in Jianfengling Nature Reserve in Hainan, China. The isolate was found to grow with 0-4 % (w/v) NaCl, at 5-40 C and pH 6.0-10.5, with an optimum of 0 % NaCl, 30-37 C and pH 8.5-9.0, respectively. The predominant isoprenoid quinone was menaquinone 7 (MK-7), and the major fatty acids were anteiso-C 15 : 0 , iso-C 16 : 0 and C 16 : 0 . The G+C content of the genomic DNA was 53.7 mol%. Analysis of the 16S rRNA gene sequence of strain DB13260 T showed an affiliation of the strain with the genus Paenibacillus, sharing 98.3 % and 97.8 % 16S rRNA gene sequence similarities with the closest relatives Paenibacillus anaericanus MH21 T and Paenibacillus selenii W126 T , respectively. The DNA-DNA hybridization values between strain DB13260 T and the two type strains were 60.4 % and 42.6 %, respectively. The combined phenotypic and DNA-DNA hybridization data supported the conclusion that strain DB13260 T represents a novel species of the genus Paenibacillus, for which the name Paenibacillus segetis sp. nov. is proposed. The type strain is DB13260 T (=CGMCC 1.12769 T =DSM 28014 T ).