Characterization of the extracellular biodemulsifiers secreted by Bacillus cereus LH-6 and the enhancement of demulsifying efficiency by optimizing the cultivation conditions

• Published in: Environmental science and pollution research international 2014-09, Vol.21 (17), p.10386-10398
• Main Authors: Hou, Ning, Feng, Fengzhao, Shi, Yan, Cao, Huiming, Li, Chunyan, Cao, Zhi, Cheng, Yi
• Format: Article
• Language: English
• Subjects: Ammonium; Ammonium sulfate; Aquatic Pollution; Atmospheric Protection/Air Quality Control/Air Pollution; Bacillus cereus; Bacillus cereus - chemistry; Bacillus cereus - metabolism; Bacteria; Biosynthesis; Biotechnology; Carbon; Carbon sources; Crude oil; Cultivation; culture media; Earth and Environmental Science; Ecotoxicology; Efficiency; Emulsions; Emulsions - metabolism; Environment; Environmental Chemistry; Environmental Health; Environmental science; Extracellular Space - metabolism; Fourier transform infrared spectroscopy; Fourier transforms; frying oil; genes; Infrared spectroscopy; Kerosene; Lipopeptides; Lipopeptides - metabolism; nitrogen; Nitrogen sources; Oil; Oils; Peptides; Petroleum; Research Article; response surface methodology; ribosomal DNA; rRNA 16S; soil; Soil contamination; Soil Microbiology; Soil pollution; Studies; Thin layer chromatography; Waste Water Technology; Water; Water Management; Water Pollution Control; Yeast; yeast extract; Yeasts
• ISSN: 0944-1344; 1614-7499
• DOI: 10.1007/s11356-014-2931-7

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.