Studies On The Screening Of A Lipopeptide Biosurfactant Producing Bacterium And Properties Of The Lipopeptide

This paper studied the screening of a biosurfactant,the properties and the safety evaluation for application.The main results were as follows:1.A series of bacteria were isolated from soil samples and water samples from Hefei University of Technology,Hefei oil storeroom and Dongying Victory scum pool from Shangdong province by a series of steps including hydrocarbon enrichment culture,hemolytic activity assay on blood agar plates and surface activity assay etc.One strain was purified and was named as H-02.It is identified as a Bacillus subtilis by biophysical and biochemical experiments according to《Bergey's Manual of Determinative Bacteriology》,16S rDNA sequence analysis. The biosurfactant produced by strain H-02 was founded as a lipopeptide biosurfactant.It has a satisfacting activity with a oil displacement diameter at 9.2 cm.Furthermore the emulsion of this lipopeptide is fine as well for maintain the emulsion for at least 10 days.2.The condition for lipopeptide production was optimized by single factor experiments and orthogonal test.Results were as follows(g/100mL):soluble starch 2.5,NH₄NO₃ 0.6,MgSO₄·7H₂O 0.04,CaCl₂ 0.008,yeast extract powder 0.08, KH₂PO₄ 0.24,Na₂HPO₄ 0.96,pH 7.0-7.5.At the inoculum of 5.0%,under 35℃, the yield of lipopeptide was 3.18 g/L.3.The physical and chemical properties of lipopeptide produced by strain H-02 was investigated.Results showed that this biosurfact produced by H-02has a excellent emulsion and vesicant characteristic,and anti-microorganisms traits just like antibiotics.So it could be used for many domains as MEOR,Food and Pharmacy. Also this lipopeptide can maintain its activity under serial extreme conditions like high temperature,high concentration salt,especially Ca²⁺ cation,and low pH.The suitable pH was identified between 4.0 and 10.0.4.The acute toxicity test and thirty days feeding study was performed,results showed that the lipopeptide has no obvious toxicity to little mouse.