Predicting the minimum liquid surface tension activity of pseudomonads expressing biosurfactants

Abstract

Numerous surveys of biosurfactant-producing bacteria have been conducted, but only recently has an attempt been made to predict the minimum liquid surface tension these surface-active agents can achieve. Here, we determine a theoretical minimum of 24 mN m(-1) by statistical analysis of tensiometry data, suggesting a fundamental limit for biosurfactant activity in bacterial cultures incubated under standard growth conditions. This raises a challenge to our understanding of biosurfactant expression, secretion and function, as well as being of interest to biotechnology where they are used in an increasingly wide range of applications.

Bio-emulsifying and biodegradation activities of syringafactin producing Pseudomonas spp. strains isolated from oil contaminated soils

“…Five isolates designated by E33b, E38b, E39, E311 and E313 were positive (Table 1) which indicated their potential to produce biosurfactants. Drop collapse assay results did not always correlate with the liquid surface tension reducing activity (Mohammed et al 2015). So, the cell-free supernatants of all isolated strains were characterised by tensiometry (Table 1).…”

“…Biosurfactants can also protect cells from toxic compounds and heavy metals by encapsulating them into micelles (Ron and Rosenberg 2001;Van Hamme et al 2006). Biosurfactant producing Pseudomonas are commonly found in different environments including soil and the rhizosphere (Fechtner et al 2011), particularly in hydrocarbon-contaminated soils where they facilitate hydrocarbon degradation (Bodour et al 2003;Bento et al 2005;D'aes et al 2010;Saikia et al 2012;Mohammed et al 2015) and on plants where they can be beneficial or harmful for their host (D'aes et al 2010). For these reasons, Pseudomonas are good candidates for discovering new biosurfactants.…”

Biofilm disruption by an air bubble reveals heterogeneous age-dependent detachment patterns dictated by initial extracellular matrix distribution

“…In our experiments, the bubble traveled at U  = 250 µm s −1 in culture medium contaminated by the presence of bacteria and EPS on the walls of the channel; in these conditions, we estimated µ  = 10 −3  Pa s and σ  = 25–50 × 10 −3 N m −1 ( see ref. 19), resulting in Ca = (5–10) × 10 −6 . For Ca << 1 the thickness of the liquid film, h , follows Bretherton's law, 20 h / H  ~ Ca 2/3 , where H  = 50 µm is the height of the microchannel and the constant of proportionality is on the order of unity.…”

Cyclic Lipodepsipeptides From Pseudomonas spp. – Biological Swiss-Army Knives

“…are able to reduce the surface tension of growth media to different extents ( Fechtner et al, 2011 ). A minimal threshold surface tension of 24.16 mN m -1 was calculated for Pseudomonas bacteria, based on a diverse set of surface tension reducing isolates ( Fechtner et al, 2011 ; Mohammed et al, 2015 ). This threshold is likely set by limits in, among others, biosynthesis and transport of surfactants out of the bacterial cell.…”