The aim of the present study was to investigate biosurfactant-producing culturable bacteria inhabiting the coast of the Arabian Sea at Karachi. Overall, 15 seawater samples were collected from the Arabian Sea coast of Karachi. Isolation, characterization, and screening for 89 biosurfactant-producing bacterial strains were conducted through 8 conventional screening tests. Through GSP agar plate method 22 strains were found to be Pseudomonas aeruginosa and Gram reaction revealed 70% of the isolates to be gramnegative. Furthermore, 24% of the isolates showed hemolytic activity, 44% exhibited positive results for oil-spreading test, 54% showed emulsification to at least 1 of the 3 hydrocarbons tested, BATH assay results indicated maximum adhesion for hexane, 52.8% produced positive results for CTAB agar plate assay, drop-collapse activity was found in 84% of the isolates, and emulsification assay revealed highest emulsification for xylene. Findings revealed none of the isolates to be negative for every screening test conducted, while only one gram-negative isolate, DGHE65, identified as Pseudomonas aeruginosa, was positive for all the tests for biosurfactant production. Results indicate that these isolates have potential for future environmental friendly applications such as bioremediation and industrial biotechnology.

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Background: The wide use of dextran in many different applications, makes its industrial production a challenge and, hence, to obtain a control branched structure of this enzyme research is in progress. Objectives: In the present paper, the enzyme dextransucrase, produced by cultivation of the bacterium Leuconostoc mesenteroides CMG713, was purified and characterized. Methods: The produced dextransucrase was partially purified by PEG400 obtaining a purification factor of 29.4-fold and an overall yield of 18.3% from the initial crude enzymatic extract. Results: The partially purified dextransucrase had a specific activity of 24.0 U/mg and presented a molecular weight of about 200 kDa. In addition, the produced dextransucrase was stable at 30ºC and pH 5.5 for 3 days and led to a highly soluble dextran with wide potential industrial applications. The current study has successfully partial purification, characterization and conformation of dextransucrase produced by fermentation of the bacterium Leuconostoc mesenteroides CMG713.