Heterologous Rhamnolipid Biosynthesis: Advantages, Challenges, and the Opportunity to Produce Tailor-Made Rhamnolipids

Abstract

The first heterologous expression of genes responsible for the production of rhamnolipids was already implemented in the mid-1990s during the functional identification of the rhlAB operon. This was the starting shot for multiple approaches to establish the rhamnolipid biosynthesis in different host organisms. Since most of the native rhamnolipid producing organisms are human or plant pathogens, the intention for these ventures was the establishment of non-pathogenic organisms as heterologous host for the production of rhamnolipids. The pathogenicity of producing organisms is one of the bottlenecks for applications of rhamnolipids in many industrial products especially foods and cosmetics. The further advantage of heterologous rhamnolipid production is the circumvention of the complex regulatory network, which regulates the rhamnolipid biosynthesis in wild type production strains. Furthermore, a suitable host with an optimal genetic background to provide sufficient amounts of educts allows the production of tailor-made rhamnolipids each with its specific physico-chemical properties depending on the contained numbers of rhamnose sugar residues and the numbers, chain length and saturation degree of 3-hydroxyfatty acids. The heterologous expression of rhl genes can also enable the utilization of unusual carbon sources for the production of rhamnolipids depending on the host organism.

Glycolipid Biosurfactants in Skincare Applications: Challenges and Recommendations for Future Exploitation

“…As with sophorolipids, assessments of the potential use of rhamnolipids in cosmetic and personal care formulations have been carried out in a number of studies [20,23]. The cytotoxicity profile of rhamnolipids extracted from Marinobacter MCTG107b and Pseudomonas MCTG214 (3b1) strains was evaluated using HaCaT and adult liver epithelial (THLE 3) cells via propidium iodide and alamar blue assays [31,68,69].…”

“…However, the pathogenicity status of P. aeruginosa (biosafety level 2 pathogen) often associated with the production of toxins, such as pyocyanin, coupled with their low yield of biosurfactants makes them less attractive for industrial applications, particularly in food and skincare products [22,106]. Consequently, several methodologies to reduce/eliminate the toxicity of P. aeruginosa via the inhibition of pyocyanin biosynthesis and the investigation of novel microorganisms and bioprocessing techniques for rhamnolipid production are currently being exploited to improve the yield of rhamnolipids and their production from non-pathogenic strains [23,104,107]. To this end, Evonik Industries has investigated and reported the large-scale production of rhamnolipids from the genetically modified and non-pathogenic P. putida KT2440 strain [41,47,108].…”

“…The most intensively studied groups of glycolipids are sophorolipids mainly produced by the yeast species Starmerella bombicola often as a crude mixture of acidic and lactonic forms and rhamnolipids mainly produced by the Gram-negative bacterium Pseudomonas aeruginosa as a crude mixture of mono-rhamnolipid and di-rhamnolipid congeners [2,20]. The biosynthetic processes, structural composition, and fermentation process/conditions of sophorolipids and rhamnolipids have been extensively investigated and reported [11,[21][22][23][24][25].…”

Rhamnolipid Biosurfactants for Oil Recovery: Salt Effects on the Structural Properties Investigated by Mesoscale Simulations

“…Although naturally produced RLs are usually in the form of mixtures of several congeners, specific congeners or tailored RLs can be synthesized currently. − The type of congeners also plays a role in hydrocarbon removal. Zhao et al used three bacterial strains to produce RL solutions with various compositions of mono-RL (mRL) and di-RL (dRL).…”

Priority changes between biofilm exopolysaccharides synthesis and rhamnolipids production are mediated by a c-di-GMP-specific phosphodiesterase NbdA in Pseudomonas aeruginosa

“…These properties are of industrial interest and have been exploited in multiple applications in the pharmaceutical, agriculture, food, detergent, and cosmetic fields. 1 , 2 , 3 Despite their broad commercial applications, their large-scale production has not been possible because of low yields and high production costs.…”