Ozonolysis of Symmetrical Bola Sophorosides Yields Key Precursors for the Development of Functional Sophorolipid Derivatives

Abstract

Sophorolipids are among the best-positioned microbial biosurfactants to reach large-scale industrial production and application. However, the structural variety of sophorolipids offered by wild-type strains is rather limited, requiring their efficient modification to expand the application areas of sophorolipids. A combination of genetic engineering and green chemical modification via ozonolysis was applied in this work to produce key precursors useful in the development of a library of sophorolipid derivatives. Uniform symmetrical α,ω-bola sophorosides, produced by a novel strain of Starmerella bombicola, were investigated as substrates for the first time to generate 100% ω-C9 sophorosides (key precursors in the development of a sophorolipid library) via ozonolysis in water. Ozonolysis yielded a mixture of C9:0 ω-sophoroside aldehydes and C9:0 ω-sophorolipid acids. The selectivity toward the C9:0 ω-sophoroside aldehyde was increased using catalase, limiting the overoxidation of the aldehyde by the in situ formed H2O2. The C9:0 ω-sophorolipid acid could be produced selectively by extending the ozonolysis time. Moreover, using water as the solvent during ozonolysis proved to be beneficial in suppressing the formation of ozonides, therefore eliminating the need to perform a reductive or oxidative workup. Consequently, an efficient, safe, and scalable route has been established for the production of key sophoroside precursors.

Tuning the antimicrobial activity of microbial glycolipid biosurfactants through chemical modification

“…The C9 sophoroside aldehyde 10 was obtained according to the previously described procedure for ozonolysis of bola sophoroside 4 in water ( Pala et al, 2022 ). The subsequent reduction of the SS aldehyde 10 with 2-picoline-borane yielded the SS alcohol 11 ( Figure 2 ).…”

A Low-Cost Ecofriendly Oxidation Process to Manufacture High-Performance Polymeric Biosurfactants Derived from Municipal Biowaste

“…So far, the R&D work on rhamnolipids and sophorolipids has attempted to improve their biosynthesis [ 53 , 54 , 55 , 56 ], while chemical technology has been mostly applied for the isolation and purification of the crude product obtained by fermentation. Chemical oxidation with O 3 and H 2 O 2 in water, combined with genetic engineering, has been applied to produce sophorolipids’ derivatives [ 58 ] in order to expand the application areas of the bacterial surfactants and establish an efficient, scalable technological basis for their competitive production at the industrial level. Still, prior to ozonolysis, most of the R&D work has been focused on genetic engineering in an attempt to reduce and simplify the multistep process for the production of the substrate to be ozonized, increase its efficiency, and reduce the end product cost.…”

"Unlocking the potential of a glycolipid platform through chemical modification"

“…The susceptibility of these functional sites on SLs have been exploited throughout the years by researchers to increase the structural variation based on classic SLs, thereby expanding the scope of potential added-value applications [8]. More recently, novel glycolipids such as bola sophorosides and glucosides [11] have been developed and investigated as alternative platform molecules for green derivatization avoiding some key issues associated with classic SLs. The synthetic approaches targeting these sites for the chemical modification of SLs, produced by both wild-type and genetically modified yeast strains, are summarized in Figure 3 and briefly discussed in the following sections.…”

“…This strategy was further improved by the same research group towards a safer, greener and a scalable process by replacing the LSL with so called symmetrical bola sophorosides (sym. bola SS) [11]. The latter was produced by a genetically modified yeast strain where two sophorose moieties are symmetrically linked to a hydrophobic linker with terminal glycosidic bonds [10].…”