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Stimulation of rhamnolipid biosurfactants production in Pseudomonas aeruginosa AK6U by organosulfur compounds provided as sulfur sources

Ismail, Wael, Shammary, Sultanah AL., El-Sayed, Wael S., Obuekwe, Christian, El Nayal, Ashraf M., Abdul Raheem, Abdul Salam, Al-Humam, Abdulmohsen
Biotechnology reports 2015 v.7 pp. 55-63
Pseudomonas aeruginosa, biosurfactants, carbon, culture media, glucose, magnesium sulfate, organic sulfur compounds, rhamnolipids, sulfur, surface tension
A Pseudomonas aeruginosa AK6U strain produced rhamnolipid biosurfactants to variable extents when grown on MgSO4 or organosulfur compounds as sulfur sources and glucose as a carbon source. Organosulfur cultures produced much higher biosurfactants amounts compared to the MgSO4 cultures. The surface tension of the growth medium was reduced from 72mN/m to 54 and 30mN/m in cultures containing MgSO4 and 4,6-dimethyldibenzothiophene (4,6-DM-DBT), respectively. AK6U cultures produced different rhamnolipid congener profiles depending on the provided sulfur source. The dibenzothiophene (DBT) culture produced more diverse and a higher number of rhamnolipid congeners as compared to the DBT-sulfone and MgSO4 cultures. The number of mono-rhamnolipid congeners in the DBT culture was also higher than that detected in the DBT-sulfone and MgSO4 cultures. Di-rhamnolipids dominated the congener profiles in all the analyzed cultures. The sulfur source can have a profound impact on the quality and quantity of the produced biosurfactants.