Abstract
Bacteria produce a variety of biosurfactants capable of significantly reducing liquid (aqueous) surface tension (γ) with a range of biological roles and biotechnological uses. In order to determine the lowest achievable surface tension (γMin), we tested a diverse collection of Pseudomonas-like isolates from contaminated soil and activated sludge, and identified those expressing biosurfactants by drop-collapse assay. Liquid surface tension reducing ability was quantitatively determined by tensiometry, with 57 isolates found to significantly lower culture supernatant surface tensions to 24.5 – 49.1 mN m−1. Differences in biosurfactant behaviour determined by foaming, emulsion and oil-displacement assays, was also observed amongst isolates producing surface tensions of 25 – 27 mN m−1, suggesting that a range of structurally-diverse biosurfactants were being expressed. Individual distribution identification (IDI) analysis was used to identify the theoretical probability distribution that best fitted the surface tension data, which predicted a γMin of 24.24 mN m−1. This was in agreement with predictions based on earlier work of published mixed–bacterial spp. data, suggesting a fundamental limit to the ability of bacterial biosurfactants to reduce surface tensions in aqueous systems. This implies a biological restriction on the synthesis and export of these agents or a physical-chemical restriction on their functioning once produced.
Original language | English |
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Pages (from-to) | 37–43 |
Number of pages | 7 |
Journal | Letters in Applied Microbiology |
Volume | 60 |
Issue number | 1 |
Early online date | 24 Sep 2014 |
DOIs | |
Publication status | Published - Jan 2015 |