Physicochemical Properties of Biosurfactants Produced from Blackstrap Molasses by a Pseudomonas aeruginosa Mutant

Zulfiqar Ali Raza, Environmental Biotechnology Division, National Institute for Biotechnology and Genetic Engineering, P.O. Box-577, Faisalabad-Pakistan. Tel: 92-41-2651475 Ext 253, Email: zarazapk@yahoo.com 
M. Saleem Khan, National Centre of Excellence in Physical Chemistry, University of Peshawar-25120, Pakistan, Tel: 92-91-9216766, Email: msalkhan@yahoo.com
Zafar M. Khalid,  Environmental Biotechnology Division, National Institute for Biotechnology and Genetic Engineering, P.O. Box-577, Faisalabad-Pakistan, Tel: 92-41-2651475 Ext 253, Email: zmklaid@yahoo.com

Biosurfactants are valuable microbial amphiphilic molecules with effective physicochemical and biological characteristics applicable to several industrial and environmental processes. In the present investigation, their production was observed when Pseudomonas aeruginosa mutant EBN-8 was grown on blackstrap molasses as primary carbon source supplemented with minimal salt media. The composition (g/L) of the media was as follow: KH₂PO₄, 1; K₂HPO₄, 1; NH₄NO₃, 1; MgSO₄.7HO₂, 0.2; CaCl.2H₂O, 0.2 and FeCl₃.6H₂O 0.05 along with varying concentrations of clarified molasses on the basis of total sugars and inoculated by 1% inoculum of EBN-8 mutant. The studies were carried out in 250-mL Erlenmeyer flasks on orbital shaker at 37^°C and 100 rpm for 22 days. The progress in the biosurfactant production was measured in terms of changes in surface and interfacial tensions, critical micelle dilution, pH, emulsification index, emulsification capacity, biomass and total sugars of the media. The biosurfactants were isolated from the culture media by acid precipitation followed by solvent extraction. The amount of rhamnolipid produced was determined by orcinol method in terms of rhamnose equivalents (RE).

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