| Biosurfactant is a natural product of surface activity produced by microbial metabolism,besides the physicochemical properties of chemical synthetic surfactants,it has the characteristics of non-toxic and easy to degrade.It has a broad application prospect in the fields of oil production,daily chemical industry,environmental treatment,food processing,medicine and other fields.This study collects soil contaminated by waste oil and oil for a long time,through enrichment culture,blue gel plate initial screening and rescreening by diameter of oil discharge circle and emulsification value in the fermentation liquid,screening a bacterium that produces biological surfactants,identification of bacterial physicochemical properties and identification of strains by 16 SrDNA sequencing.Mutagenesis and breeding of the screened bioactive agent produced by nitroguanidine,and optimization of mutant strain fermentation conditions by single factor test and L9(34)orthogonal test.Biosurfactant was extracted by acid precipitation combined with organic solvent extraction,and silica gel(200-300 mesh)and Sephadex G-15 gel column chromatography were used to purify biological surfactant..The types of products were identified by TLC.The components and contents of biological surfactant were analyzed by mass spectrometry and high performance liquid chromatography,and the structure of bio surfactant was characterized by IR,carbon and hydrogen spectrum.The surface activity of the surfactant,the critical micelle concentration(CMC),the emulsifying property and the bacteriostasis activity of the surface active agent were compared.The best formula of biosurfactant blank microemulsion was determined by the single factor test,and test its stability,finally carrying on the application effect of gingerol microemulsion system in centrifugal,high and low temperature and pH conditions were evaluated.The results of the study are as follows:(1)A biosurfactant Producing Strain JZ-5 was screened from 16 soil samples collected.It was identified as Pseudomonas aeruginosa by physicochemical property identification and 16 SrDNA sequence analysis.A high yield and stable genetic strain JZ-5M6 was obtained through mutation breeding of nitroguanidine.The yield of the mutant strain reached 40.83 g/L,which was 50.84% higher than that of the original strain.(2)The results of single factor test showed that the factors affecting the fermentation conditions of mutant strain JZ-5M6 were carbon source,nitrogen source and inoculation amount.The conditions of the mutant strain produced by the L9(34)orthogonal experiment are as follows: glucose 20g/L,sodium nitrate 2g/L,and inoculation amount 70mL/L.(3)The bioactive agent BH produced by the mutant strain JZ-5M6 was identified as glycolipid by thin layer chromatography,and the sugar group was divided into Li Tang.After testing,rhamnolipid contained 6 components,and the highest content of BH-1 was purified by two times,and its molecular structure was determined by IR and NMR..The surface tension of water can be reduced from 72mN/m to about 25mN/m by BH,and its CMC value is 15mg/L.The 24 h emulsification value of BH for the water liquid paraffin wax system is 67.5%,and the emulsified layer formed in the water liquid paraffin system is stable in 3 months.BH showed good antibacterial activity to Escherichia coli,Staphylococcus aureus and Bacillus subtilis.The bacteriostasis performance was better than that of Twain 80,SDS and sanfatia.(4)Through the monomer drop method,the best formula of the blank microemulsion system with BH as surfactant is determined as follows: oleic acid /BH/ polyethylene glycol / water,the ratio of surfactant to cosurfactant,Km value is 1:1.The pH of the blank microemulsion prepared at 10%,20%,30%,40%,50% and 60%,respectively,was about 6.2,showing weak acidity and surface tension all around 30mN/N.Prepared based on the blank microemulsion on gingerol loaded microemulsion in centrifugal,high and low temperature and pH conditions showed good stability. |
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