iBB

The use of Mannosylerythritol lipids (MELs), a group of biosurfactants with excellent biochemical properties, in bioremediation in marine and terrestrial environments has been envisioned. However, knowledge regarding their ecotoxicity is limited, and the current production costs are too high to make them competitive in the surfactant market. In an effort to facilitate the use of MELs for marine bioremediation purposes, the team from 2BRG/iBB studied MELs production using seawater in medium formulation as reported on “Towards Mannosylerythritol Lipids (MELs) for Bioremediation: Effects of NaCl on M. antarcticus Physiology and Biosurfactant and Lipid Production; Ecotoxicity of MELs”, published in Journal of Marine Science and Engineering. The cells were exposed to different levels of NaCl during fermentation and the effects of increased salinity on the cells and their performance were monitored. In addition, the cells were briefly exposed to osmotic shock by introducing pure NaCl into the broth to measure their physiological responses. Although the overall effect of NaCl in the medium was negative, cells produced more lipases in these stress conditions. Furthermore, the changes triggered by osmotic shock caused changes in the cell surface and affected their hydrophobicity, reducing the levels of MELs adsorbed to the cells, which in turn led to an increase in the formation of MEL-rich beads. Marine-level salinity (3.5%) was found to be sufficient to enable the production of MELs under non-sterile conditions and to inhibit the introduction of bacterial contaminants. Finally, the toxicity levels of MELs in a model marine organism and plant model were lower than those of other biosurfactants and a commercial chemical dispersant used for bioremediation.

This publication has as first-author the (now former) PhD student Petar Kekovic of the MIT-Portugal Program in Bioengineering - and as a corresponding author Frederico Ferreira and Nuno Faria.  Additionally, the co-authors and a team from Sintef – Roman Netzer, Umer Farooq and Ariadna Szczybelski submitted a patent application for formulation of a novel MEL based oils spill response agent, reference number 117583.

A biological process for the production of xylonic acid (XA) from xylose or from xylose-rich lignocellulosic hydrolysates has been patented by BERG-iBB researchers Teresa Cesário, Manuela Fonseca and Maryna Bondar (PT 115970). The ability of the wild strain Paraburkholderia sacchari (previously classified as Burkholderia sacchari) DSM 17165 to produce xylonic acid from renewable and sustainable feedstocks is claimed. XA is a potential substitute for gluconic acid (GA), namely in the pharma industry, as a chelating agent, as a precursor of 1,2,4-butanetriol, polyamides and polyesters, as well as in the production of solvents, paints, adhesives and dyes. Moreover, XA, like GA, can be used as a retardant of the setting time of cement paste. XA productivities in the range 4.8 g/(L.h) to 7.1 g/(L.h) and yields between 89% e 100% were achieved, with XA titres of 360 to 390 g/L, using one single, non-pressurised stirred tank reactor operating in the fed-batch mode under dissolved oxygen concentrations higher than 10%  saturation.