Development of a Cradle-to-Grave Approach for Acetylated Acidic Sophorolipid Biosurfactants

International audienceMicrobial production of biosurfactants represents one of the most interesting alternatives to classical petrol-based compounds due to their low toxicity, high biodegradability, and biological production processes from renewable bioresources. However, some of the main drawbacks generally encountered are the low productivities and the small number of chemical structures available, which limit widespread application of biosurfactants. Although chemical derivatization of (microbial) biosurfactants offers opportunities to broaden the panel of available molecules, direct microbial synthesis is still the preferred option and the use of engineered strains is becoming a valid alternative. In this multidisciplinary work we show the entire process of conception, upscaling of fermentation (150 L) and sustainable purification (filtration), application (foaming, solubilization, antibacterial), and life cycle analysis of acetylated acidic sophorolipids, directly produced by the Starmerella bombicola esterase knock out yeast strain, rather than purified using chromatography from the classical, but complex, mixture of acidic and lactonic sophorolipids

Microbial biosurfactants : from lab to market

Biosurfactants have been the subject of an impressive amount of research efforts, both by academia as by the industry. Two major factors that have been limiting real commercialization of biosurfactants in the past are firstly the limited structural variety and secondly the high production price due to low inherent productivities, small scale and/or a lack of process knowledge. A solution can be offered by an integrated process design (IPD) approach, where the entire innovation chain is taken into account. Genetic engineering on one side of the spectrum generates new strains, which are subsequently subjected to thorough investigation of the production processes, with feedback coupling to the strain level. Subsequent scale up on one hand enables assessing the scalability of the processes and performing techno-economical and LCA analyses, but on the other hand also results in the generation of kg scale biosurfactant samples of high purity. The availability of such large amounts of a portfolio of molecules enables thorough application research of the new molecules and their derivatives in a vast variety of sectors. This approach has been applied for one of the showcases of biosurfactant production: the yeast Starmerella bombicola. The development of a molecular toolbox enabled the generation of several new S. bombicola strains, efficiently producing new-to-nature biosurfactants. These new strains were subjected to an iterative optimization process, while the production processes (fermentation and purification) for each new biomolecule/strain were investigated in parallel. Dedicated application research identified possible valorization options and a business case for the commercialization was recently finalized. The combination of these efforts is expected to result in real market penetration of these molecules in the near future

Sophorolipid amine oxide production by a combination of fermentation scale-up and chemical modification

Production scale-up of high-purity diacetylated C18:1 sophorolipid lactone was demonstrated from lab to pilot scale with the Starmerella bombicola lactone esterase overexpression strain (oe sble) as producing organism. The 150 L fermentation using oleic acid and yeast extract, characterized by a titer of 199 g/L and a volumetric productivity of 0.9 g/Lh, was most successful in obtaining a highly pure (>98%) and uniform (96% C18:1 SL lactone) sophorolipid product suitable for chemical derivatization. The fermentation product was subsequently modified to produce sophorolipid amine oxides, which cannot be produced enzymatically. First, the fermentation product was transformed into an intermediate sophorolipid aldehyde via methanolysis and protection of the sugar head through acetylation and ozonolysis. This aldehyde intermediate was then used for the synthesis of the sophorolipid amine oxides via reductive amination, oxidation, and deprotection of the sugar head. The total yield of this synthetic pathway amounts to 18-30%. These compounds constitute a class of innovative sophorolipid derivatives with potential for high added-value applications. The sophorolipid amine oxides have been evaluated for their antimicrobial activity against the Gram-negative bacteria Escherichia coli LMG 8063, Klebsiella pneumoniae LMG 2095, and Pseudomonas aeruginosa PAO1 and the Gram-positive bacteria Staphylococcus aureus ATCC 6538 and Staphylococcus auereus Mu50. The present approach of combining large-scale fermentation and subsequent chemical modification facilitates the creation of a platform of innovative sophorolipid derivatives in adequate quantities, opening the door for novel applications

Microbial biosurfactants : from lab to market: hurdles and how to take them

Biosurfactants have been the subject of an impressive amount of research efforts, both by academia as by the industry. Two major factors that have been limiting real commercialization of biosurfactants in the past are firstly the limited structural variety and secondly the high production price due to low inherent productivities, small scale and/or a lack of process knowledge. A solution can be offered by an integrated process design (IPD) approach, where the entire innovation chain is taken into account. Genetic engineering on one side of the spectrum generates new strains, which are subsequently subjected to thorough investigation of the production processes, with feedback coupling to the strain level. Subsequent scale up on one hand enables assessing the scalability of the processes and performing techno-economical and LCA analyses, but on the other hand also results in the generation of kg scale biosurfactant samples of high purity. The availability of such large amounts of a portfolio of molecules enables thorough application research of the new molecules and their derivatives in a vast variety of sectors. This approach has been applied for one of the showcases of biosurfactant production: the yeast Starmerella bombicola. The development of a molecular toolbox enabled the generation of several new S. bombicola strains, efficiently producing new-to-nature biosurfactants. These new strains were subjected to an iterative optimization process, while the production processes (fermentation and purification) for each new biomolecule/strain were investigated in parallel. Dedicated application research identified possible valorization options and a business case for the commercialization was recently finalized. The combination of these efforts is expected to result in real market penetration of these molecules in the near future