Capacity for biosurfactant production of environmental Pseudomonas and Vibrionaceae growing on carbohydrates

Summary Pseudomonas and Vibrionaceae strains with the capacity to produce biosurfactants when growing on sucrose were isolated from the environment by a simple screening procedure. Agargrown colonies were randomly selected; each colony was suspended in a water droplet on a microscope slide. The tested strain was regarded as positive if the droplet spread over the surface.1779 Pseudomonas and 660 Vibrionaceae isolates were tested; 1% and 0.8% of the isolates, respectively, were positive for biosurfactant production. No production was detected amongst the isolates of a control group of 538 Gram-positive and 1063 Gram-negative strains.Four biosurfactant producing strains were grown in fermenter cultures on a semisynthetic medium using sucrose as carbon and energy source. The terminal concentrations of biosurfactants were in the range of a factor 40 times the critical micelle dilution. One P. fluorescens strain was grown in a carbon limited chemostat (succinate). The biosurfactant production was successively decreasing until it stopped after less than ten generation times.