Heterologous rhamnolipid producers based on Acetobacter aceti AlC1824 obtaining
M.N. Baramzin, S.G. Litvinets
Section: Chemistry of natural environments and objects
Rhamnolipids solubilize oil contaminants in soils, making them more accessible for decomposition by soil microorganisms. Unlike chemical surfactants, rhamnolipids are environmentally friendly. The aim of this work is to obtain heterologous rhamnolipid producers based on Acetobacter aceti AlC1824 using an artificial promoter and optimize the producer cultivation conditions. This approach will avoid the use of highly effective biosurfactants of the opportunistic Pseudomonas aeruginosa species as a rhamnolipid producer, which can be used for soil bioremediation. The rhlAB gene cluster was amplified from the Pseudomonas aeruginosa B-6643 genome by polymerase chain reaction. A construct consisting of the rhlAB gene cluster and an artificial promoter was inserted into the p-AlT2 vector. The insert was introduced into Acetobacter aceti AlC1824 cells by calcium transformation. A total of 20 transformants were selected by blue-white selection. The target insert was detected in 7 transformants by polymerase chain reaction. The indicator test revealed a characteristic precipitate in two transformants: A4 and A8. Glucose, mannitol and glycerol were used as substrates. Suitable nitrogen and carbon sources were determined: peptone and mannitol, respectively. We found that the overall optimal pH of the medium was 5; the optimal cultivation temperature was 30 оC for A4 and 25 оC for A8. The amount of rhamnolipids formed by the above in optimal conditions is 139.3±20.1 mg/mL for transformant A4 and 13.0±1.0 mg/mL for transformant A8. The high washrhamnolipid emulsifying activity of heterologous producers in relation to crude oil has been experimentally demonstrated: EI24 for A4 was 93,9±1,5%, and for A8 – 96,7±1,5%.
ISSN 1995-4301
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