| Pseudomonas aeruginosa could secrete rhamnolipid biosurfactant which has potential to be widely used in varius industrial fields especially dealing with hydrocarbon pollutions.This study screened high rhamnolipid producing strains from sevral source and analyzed their oil degrading abilities.CTAB-methylene blue plate was used as primary screen method to isolated rhamnolipid producing strains from laboratory,environment soil,crude oil and oil polluted soil samples.The strains with a dark blue halo around the colony were chosed and then analyzed rhamnolipid production by anthrone-sulfuric acid method.We obtain 13 high yield strains,with rhamnlpid production of 10.3-18.9 g/L and 2 strains isolated from crude oil and oil polluted soil with the production of 9.5 g/L and 4.2 g/L.13 high yield strains and 2 oil-origin strains were identified by physiological and biochemical tests and 16S rRNA.The identities of their 16S rRNA sequence with Pseudomonas aeruginosa are 99%-100%,so we confirm that 15 strains are all Pseudomonas aeruginosa.Glycerol and rapeseed oil were used as carbon resorce in production of rhamnolipid by 15 strains.The results indicated that rapeseed oil is better carbon source in producing more rhamnolipid than that when glycerol as carbon source.Rapeseed oil and NaNO3 concentration were optimized for strain A487,and rhamnolipid production increased by23.4%and 16.1%.The fermentation temperature was optimized,results show that 37℃ is better for both bacterial growth and secretion of rhamnolipid.P.aeruginosa D1 and P.aeruginosa E1 were analyzed to grow on some hydrocarbons.The results show that P.aeruginosa D1 could grew on crude oil and diesel,the cell population was increased to 4.7×109 and 4.0×109 cfu/mL respectively,strain E1 could grew on crude oil,the cell population was increased to 2.7×108 cfu/mL.P.aeruginosa D1 was cultured in mineral basal medium with 1 g crude oil per liter,part of media was added 0.5 g/L glycerol.After 10 days of incubation,the concentration of crude oil dropped from 0.78 g per liter to 0.50 g per liter,while concentration of the medium added with glycerol dropped from 0.78 g per liter to 0.22 g per liter.Colony-counting analysis of s1rain D1 show that cell population increased to 4.8×109 cfu/mL after 4 d in crude oil media,while in media with addition of glycerol,cell population increased to 9.2×109 cfu/mL after 4d.The addition of glycerol could promote the growth and promote crude oil degradation. |
