Rhamnolipids are conserved biosurfactants molecules: implications for their biotechnological potential

Abstract

A range of isolates of Pseudomonas aeruginosa from widely different environmental sources were examined for their ability to synthesise rhamnolipid biosurfactants. No significant differences in the quantity or composition of the rhamnolipid congeners could be produced by manipulating the growth conditions. Sequences for the rhamnolipid genes indicated low levels of strain variation, and the majority of polymorphisms did lead to amino acid sequence changes that had no evident phenotypic effect. Expression of the rhlB and rhlC rhamnosyltransferase genes showed a fixed sequential expression pattern during growth, and no significant up-regulation could be induced by varying producer strains or growth media. The results indicated that rhamnolipids are highly conserved molecules and that their gene expression has a rather stringent control. This leaves little opportunity to manipulate and greatly increase the yield of rhamnolipids from strains of P. aeruginosa for biotechnological applications.

Development and validation of an ultra-performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS) method for the quantitative determination of rhamnolipid congeners

“…The use of these colorimetric methods overestimates RL yields and is not a true representation of the kinetics of RL production, i.e., carbon source/biomass to RL yield, particularly when these carbon sources are carbohydrate or glycerol based. Perfumo et al (2013) reported that using the orcinol assay to quantify RLs led to a significant overestimation of actual yields when coupled with the conversion factor to incorporate the fatty acid moiety of RLs. Indeed, even quantifying RLs based on extraction yields can be unreliable due to excess carbon source and other impurities such as HAAs being co-extracted and reported as RLs.…”

Microbiotechnology Based Surfactants and Their Applications

“…In a recent molecular biology investigation (Perfumo et al, 2013) for the expression of the rhlB and rhlC rhamnosyltransferase genes responsible for RHLs production of P. aeruginosa strains showed no significant differences in the genes or the quantity or composition of RHLs congeners obtained by manipulating growth conditions. Fixed sequential expression patterns for rhlB and rhlC rhamnosyltransferase genes were observed during growth.…”

“…They used 24 full factorial experimental design, using temperature, glucose concentration from cashew apple juice, phosphorous concentration and cultivation time as variables. Kinetics of growth and production of BSs by P. aeruginosa indicated reduction in SFT up to 47.7 to 28.0 dyn/cm and indicated production of surface active molecules.In a recent molecular biology investigation (Perfumo et al, 2013) for the expression of the rhlB and rhlC rhamnosyltransferase genes responsible for RHLs production of P. aeruginosa strains showed no significant differences in the genes or the quantity or composition of RHLs congeners obtained by manipulating growth conditions. Fixed sequential expression patterns for rhlB and rhlC rhamnosyltransferase genes were observed during growth.…”

The Definition, Preparation and Application of Rhamnolipids as Biosurfactants

“…In recent years, attention has been diverted toward biosurfactants because of their broad range of functional properties and renewable production routes based on microbes56. Rhamnolipids are powerful natural emulsifiers, can reduce the surface tension of water, can be used to assist in the breakdown and removal of oil spills, and have well-defined roles in medical and agricultural fields due to their antibacterial, antimicrobial, and antifungal properties [57]. Rhamnolipids biosurfactants can be applied to several industrial sectors, including the handling of industrial emulsions, controlling oil spills, biodegradation, detoxification of industrial effluents, bioremediation of contaminated soil, and in the production of biocompatible cosmetic products [58][59].…”