Synthesis of bolaform biosurfactants by an engineered Starmerella bombicola yeast

Abstract

Bola-amphiphilic surfactants are molecules with fascinating properties. Their unique configuration consisting of a long hydrophobic spacer connecting two hydrophilic entities renders the molecule more water soluble than the average surfactant, but still allows formation of supramolecular structures. These properties make them extremely suitable for applications in in nanotechnology, electronics, and gene and drug delivery. In general, these compounds are obtained by chemical synthesis. We report here an efficient microbial production process for the fully green synthesis of bolaform surfactants. A sophorolipid-producing Starmerella bombicola yeast strain was disabled in its sophorolipid acetyltransferase and lactone esterase, which should logically result in synthesis of non-acetylated acidic sophorolipids; molecules with the classic amphiphilic structure. Surprisingly, also bolaform glycolipids were obtained, with an additional sophorose linked to the free carboxyl end of the acidic sophorolipids as confirmed by MS and NMR analysis. The obtained titers of 27.7 g/L total product are comparable to wild type values, and the novel molecules account for at least 74% of this. Bola-amphiphile biosynthesis proved to be attributed to the promiscuous activity of both UDP-glucosyltransferases UGTA1 and UGTB1 from the core sophorolipid pathway, displaying activity toward non-acetylated intermediates. The absence of acetyl groups seems to trigger formation of bolaform compounds starting from acidic sophorolipids. Hence, wild type S. bombicola produces these compounds only at marginal amounts in general not reaching detection limits. We created a strain knocked-out in its sophorolipid acetyltransferase and lactone esterase able to produce these novel compounds in economical relevant amounts, opening doors for the application of biological-derived bolaform structures. Biotechnol. Bioeng. 2016;113: 2644-2651. © 2016 Wiley Periodicals, Inc.

Unraveling and resolving inefficient glucolipid biosurfactants production through quantitative multiomics analyses of Starmerella bombicola strains

“…The final titer of the original ∆ ugtB1 :: URA3 G9 strain, amounted to only 3 g/L, while that of the ∆ ugtB1 :: URA3 PT36 strain reached 27 g/L (Figure a). This was similar to glycolipid production values for other engineered S. bombicola strains as for the production of acidic SL's (Roelants et al, ), nonsymmetrical bolaform sophorolipids (Van Bogaert et al, ) and symmetrical bolaform sophorosides (Van Renterghem et al, ).…”

“…This yeast also has inherent potential as “chassis” organism for the production of other industrially relevant (glyco)lipid compounds, due to its highly efficient native glycolipid machinery, efficient acetyl‐CoA, and uridine diphosphate glucose (UDP)‐glucose machinery and its resistance to (high amounts) of hydrophobic/antibiotic compounds (Van Bogaert, De Maeseneire, Develter, Soetaert, & Vandamme, ; Van Bogaert, Fleurackers, Van Kerrebroeck, Develter, & Soetaert, ) and efficient uptake/secretion systems for hydrophobic and amphiphilic compounds. In the past, the natural SL production of this yeast production has already been extended toward the production of different (new‐to‐nature) biochemicals by strain engineering (Roelants et al, ; Roelants et al, ; Soetaert, De Maeseneire, Saerens, Roelants, & Van Bogaert, ; Van Bogaert, Buyst, Martins, Roelants, & Soetaert, ; Van Renterghem et al, ). However, some of these novel strains are showing severe productivity drops compared with the very efficient wild type SL production (Roelants et al, ; Saerens, Saey, & Soetaert, ; Saerens, Zhang, Saey, Van Bogaert, & Soetaert, ) without clear cause.…”

Biosurfactants from Waste: Structures and Interfacial Properties of Sophorolipids Produced from a Residual Oil Cake

“…To expand the market for SL, research should be focused on the improvement of their cost performance relative to existing commercial surfactants, which determines their commercial viability (Marchant and Banat, ). This goal can be achieved by adopting different strategies such as the use of cheaper renewable feedstocks or even waste materials as substrates (Jiménez‐Peñalver et al, ; Maddikeri et al, ), the use of novel or modified strains to improve production (Van Bogaert et al, , ), or the synthesis of modified SL with better biological and physicochemical properties than natural SL (Peng et al, ; Zhang et al, ). The fermentation and downstream strategies and bioreactor design also have a tremendous impact on productivity, and solid‐state fermentation shows an interesting potential, allowing for the use of solid insoluble wastes as substrates (Wang et al, ).…”

Yeast glycolipid biosurfactants

“…Second, lack of acetyl groups improves water solubility, essential for the detergent industry. Looking at the SL biosynthesis pathway, one would assume that simple knockout of acetyltransferase ( at ) would provide such nonacetylated SLs; however, knocking out this enzyme led to the production of not only nonacetylated SLs but – rather unexpectedly – also SLs with carbohydrate head groups on both sides, so‐called bolaamphiphilic SLs .…”

“…While exclusive production of the former SLs can be achieved in concentrations comparable to the wild‐type strain by S. bombicola Δ sble , the strain overexpressing sble secretes over 99% of lactonic SLs (in comparison to 57% in wild‐type mixture) in even higher concentration then a wild‐type strain. In order to bring the SL complexity even further down, both sble and at knockout were combined into one strain . As a result, the production broth again contained these intriguing bolaamphiphilic SLs, identical as for the Δ at S. bombicola , not the expected nonacetylated acidic SLs.…”