Biomonitoring of biosurfactant production by green fluorescent protein‐marked Bacillus subtilis W1012

BACKGROUND: Biosurfactant production was investigated using two strains of Bacillus subtilis , one being a reference strain ( B. subtilis 1012) and the other a recombinant of this ( B. subtilis W1012) made able to produce the green fluorescent protein (GFP). RESULTS: Batch cultivations carried out at different initial levels of glucose ( G 0 ) in the presence of 10 g L −1 casein demonstrated that the reference strain was able to release higher levels of biosurfactants in the medium at 5.0≤ G 0 ≤10 g L −1 ( B max = 104–110 mg L −1 ). The recombinant strain exhibited slightly lower levels of biosurfactants ( B max = 90–104 mg L −1 ) but only at higher glucose concentrations ( G 0 ≥ 20 g L −1 ). Under these nutritional conditions, the fluorescence intensity linked to the production of GFP was shown to be associated with the cell concentration even after achievement of the stationary phase. CONCLUSION: The ability of the genetically‐modified strain to simultaneously overproduce biosurfactant and GFP even at low biomass concentration makes it an interesting candidate for use as a biological indicator to monitor indirectly the biosurfactant production in bioremediation treatments. Copyright © 2008 Society of Chemical Industry