Production and separation of a trehalolipid biosurfactant

This paper reports on a study of the foaming characteristics of trehalolipid biosurfactants in fermentation broths and the utilisation of foaming to enable product recovery. Trehalolipids were produced by a recently isolated marine bacterium, Rhodococcus sp. PML026, in shake flasks and bioreactors. Fermentations were conducted with hexadecane as the carbon substrate. Hexadecane is an antifoam agent which supresses foam formation during fermentation, an advantageous effect during the growth and production phases. The aim of this work was to improve trehalolipid production and identify a suitable media formulation and process conditions to ensure the hexadecane substrate was depleted by the end of the fermentation to enable foaming to occur, allowing for product separation by foam fractionation. The results show that at a threshold biosurfactant concentration and with a residual amount of hexadecane vigorous foaming of the broth commenced in the bioreactor. Foam overflowed through the bioreactor condenser exit was found to separate 23–58% of the total trehalolipids with a product enrichment of 2.3–1.4. This study demonstrates for the first time a potential inexpensive and environmentally friendly strategy to separate trehalolipids from an emulsified fermentation broth

Sophorolipid biosurfactants: Possible uses as antibacterial and antibiofilm agent

Biosurfactants are amphipathic, surface-active molecules of microbial origin which accumulate at interfaces reducing interfacial tension and leading to the formation of aggregated micellular structures in solution. Some biosurfactants have been reported to have antimicrobial properties, the ability to prevent adhesion and to disrupt biofilm formation. We investigated antimicrobial properties and biofilm disruption using sophorolipids at different concentrations. Growth of Gram negative Cupriavidus necator ATCC 17699 and Gram positive Bacillus subtilis BBK006 were inhibited by sophorolipids at concentrations of 5% v/v with a bactericidal effect. Sophorolipids (5% v/v) were also able to disrupt biofilms formed by single and mixed cultures of B. subtilis BBK006 and Staphylococcus aureus ATCC 9144 under static and flow conditions, as was observed by scanning electron microscopy. The results indicated that sophorolipids may be promising compounds for use in biomedical application as adjuvants to other antimicrobial against some pathogens through inhibition of growth and/or biofilm disruption