20 research outputs found
Palmitic Acid Sophorolipid Biosurfactant: From Self-Assembled Fibrillar Network (SAFiN) To Hydrogels with Fast Recovery
Nanofibers are an interesting phase into which amphiphilic molecules can
self-assemble. Described for a large number of synthetic lipids, they were
seldom reported for natural lipids like microbial amphiphiles, known as
biosurfactants. In this work, we show that the palmitic acid congener of
sophorolipids (SLC16:0), one of the most studied families of biosurfactants,
spontaneously forms a self-assembled fiber network (SAFiN) at pH below 6
through a pH jump process. pH-resolved in-situ Small Angle X-ray Scattering
(SAXS) shows a continuous micelle-to-fiber transition, characterized by an
enhanced core-shell contrast between pH 9 and pH 7 and micellar fusion into
flat membrane between pH 7 and pH 6, approximately. Below pH 6, homogeneous,
infinitely long nanofibers form by peeling off the membranes. Eventually, the
nanofiber network spontaneously forms a thixotropic hydrogel with fast recovery
rates after applying an oscillatory strain amplitude out of the linear
viscoelastic regime (LVER): after being submitted to strain amplitudes during 5
min, the hydrogel recovers about 80% and 100% of its initial elastic modulus
after, respectively, 20 s and 10 min. Finally, the strength of the hydrogel
depends on the medium's final pH, with an elastic modulus fivefold higher at pH
3 than at pH 6.Comment: Philosophical Transactions of the Royal Society of London. A
(1887--1895), Royal Society, The, In pres
Increasing uniformity of biosurfactant production in Starmerella bombicola via the expression of chimeric cytochrome P450s
Sophorolipids are one of the best known microbial biosurfactants and are produced by several yeast species. The best studied producer is Starmerella bombicola, a non-pathogenic yeast associated in nature with bumblebees. Sophorolipids are built up of the rare disaccharide sophorose, which is attached to a fatty acid through a glyosidic bound. Sophorolipids produced by S. bombicola mainly contain oleic acid as the incorporated hydrophobic group. Other chain lengths can, to a certain content, be incorporated by feeding the yeast with substrates of alternative chain lengths. However, the efficiency for such substrates is low as compared to the preferred C18 chain length and defined by the substrate specificity of the first enzymatic step in sophorolipid biosynthesis, i.e., the cytochrome P450 enzyme CYP52M1. To increase product uniformity and diversity at the same time, a new strain of S. bombicola was developed that produces sophorolipids with a palmitic acid acyl chain. This was achieved by heterologous expression of the cytochrome P450 cyp1 gene of Ustilago maydis and feeding with palmitic acid. Optimization of the production was done by protein and process engineering
Increasing Uniformity of Biosurfactant Production in Starmerella bombicola via the Expression of Chimeric Cytochrome P450s
Sophorolipids are one of the best known microbial biosurfactants and are produced by several yeast species. The best studied producer is Starmerella bombicola, a non-pathogenic yeast associated in nature with bumblebees. Sophorolipids are built up of the rare disaccharide sophorose, which is attached to a fatty acid through a glyosidic bound. Sophorolipids produced by S. bombicola mainly contain oleic acid as the incorporated hydrophobic group. Other chain lengths can, to a certain content, be incorporated by feeding the yeast with substrates of alternative chain lengths. However, the efficiency for such substrates is low as compared to the preferred C18 chain length and defined by the substrate specificity of the first enzymatic step in sophorolipid biosynthesis, i.e., the cytochrome P450 enzyme CYP52M1. To increase product uniformity and diversity at the same time, a new strain of S. bombicola was developed that produces sophorolipids with a palmitic acid acyl chain. This was achieved by heterologous expression of the cytochrome P450 cyp1 gene of Ustilago maydis and feeding with palmitic acid. Optimization of the production was done by protein and process engineering
Biotechnological opportunities in biosurfactant production
In the recent years, biosurfactants proved to be an interesting alternative to petrochemically derived surfactants. Two classes of biosurfactants, namely glycolipids and lipopeptides, have attracted significant commercial interest. Despite their environmental advantages and equal performance, commercialization of these molecules remains a challenge due to missing acquaintance of the applicants, higher price and lack of structural variation. The latter two issues can partially be tackled by screening for novel and better wild-type producers and optimizing the fermentation process. Yet, these traditional approaches cannot overcome all hurdles. In this review, an overview is given on how biotechnology offers opportunities for increased biosurfactant production and the creation of new types of molecules, in this way enhancing their commercial potential