| Summary: | 碩士 === 國立成功大學 === 化學工程學系碩博士班 === 93 === Rhamnolipid is a glycolipid-type biosurfactant primarily produced by Pseudomonas aeruginosa strains. Pseudomonas aeruginosa J4 was isolated from the wastewater of Kaohsiung petrochemical plant. Rhamnolipid can reduce surface tension of water from 72 to 29 dyne/cm. The critical micelle concentration of rhamnolipid is 40 mg/L and the critical emulsion index of kerosene and diesel are 55 mg/L and 100 mg/L, respectively. The emulsification index against kerosene or diesel is 80%. Also, rhamnolipid has good thermal stability and is resistant to elevated temperatures.
We investigated the effects on medium compositions, temperature, agitation and carbon sources. Response surface methodology was used to identify optimal mineral salt composition for rhamnolipid production. The optimal medium compositions of maximum rhamnolipid production were 8% olive oil, 50 mM NH4NO3, 4.28 mM Na2HPO4, 30 mM KH2PO4, 257.53 �嵱 MgSO4˙7H2O, 7�n�嵱 CaCl2, 4�n�嵱 sodium EDTA, 1.14�n�嵱 FeSO4˙7H2O. The optimal cultural conditions were temperature 37 oC, agitation rate 200 rpm and pH 7.0. Under these optimal conditions, the maximum rhamnolipid production was 8.6 g/L. In addition, the yield of rhamnolipid was improved by adding solid carriers (such as cylindrical activated carbon and expanded clay) and by using immobilized cells. The results show that addition of solid carriers could stimulate cell growth. The optimal additions of expanded clay and cylindrical activated carbon were 93.3 g/L and 26.7 g/L. Those condition would obtain rhamnolipid production were 16.3 g/L and 15.3 g/L, respectively.
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