Biosurfactants, natural alternatives to synthetic surfactants: Physicochemical properties and applications

Rhamnolipids are a class of biosurfactants which contain rhamnose as the sugar moiety linked to β-hydroxylated fatty acid chains. Rhamnolipids can be widely applied in many industries including petroleum, food, agriculture and bioremediation etc. Pseudomonas aeruginosa is still the most competent producer of rhamnolipids, but its pathogenicity may cause safety and health concerns during large-scale production and applications. Therefore, extensive studies have been carried out to explore safe and economical methods to produce rhamnolipids. Various metabolic engineering efforts have also been applied to either P. aeruginosa for improving its rhamnolipid production and diminishing its pathogenicity, or to other non-pathogenic strains by introducing the key genes for safe production of rhamnolipids. The three key enzymes for rhamnolipid biosynthesis, RhlA, RhlB and RhlC, are found almost exclusively in Pseudomonas sp. and Burkholderia sp., but have been successfully expressed in several non-pathogenic host bacteria to produce rhamnolipids in large scales. The composition of mono- and di-rhamnolipids can also be modified through altering the expression levels of RhlB and RhlC. In addition, cell-free rhamnolipid synthesis by using the key enzymes and precursors from non-pathogenic sources is thought to not only eliminate pathogenic effects and simplify the downstream purification processes, but also to circumvent the complexity of quorum sensing system that regulates rhamnolipid biosynthesis. The pathogenicity of P. aeruginosa can also be reduced or eliminated through in vivo or in vitro enzymatic degradation of the toxins such as pyocyanin during rhamnolipid production. The rhamnolipid production cost can also be significantly reduced if rhamnolipid purification step can be bypassed, such as utilizing the fermentation broth or the rhamnolipid-producing strains directly in the industrial applications of rhamnolipids.

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Microbial production of rhamnolipids: opportunities, challenges and strategies

The objective of this review is to provide a comprehensive overview of the advances in the applications of rhamnolipids biosurfactants in soil and ground water remediation for removal of petroleum hydrocarbon and heavy metal contaminants. The properties of rhamnolipids associated with the contaminant removal, that is, solubilization, emulsification, dispersion, foaming, wetting, complexation, and the ability to modify bacterial cell surface properties, were reviewed in the first place. Then current remediation technologies with integration of rhamnolipid were summarized, and the effects and mechanisms for rhamnolipid to facilitate contaminant removal for these technologies were discussed. Finally rhamnolipid-based methods for remediation of the sites co-contaminated by petroleum hydrocarbons and heavy metals were presented and discussed. The review is expected to enhance our understanding on environmental aspects of rhamnolipid and provide some important information to guide the extending use of this fascinating chemical in remediation applications.

Advances in applications of rhamnolipids biosurfactant in environmental remediation: A review

A review on biosurfactants: properties, applications and current developments.

Effects of rhamnolipids on microorganism characteristics and applications in composting: A review

To be competitive with common chemical surfactants, the cost of rhamnolipid production must be minimized by selecting suitable substrates and optimizing the fermentation process. With different plant oils as substrates, Pseudomonas aeruginosa TIB-R02 can produce rhamnolipids with different structural characteristics that were confirmed by HPLC/MS analysis. Different rhamnolipids had different performances in interfacial tension. The production of rhamnolipid was greatly enhanced by fermentation optimization with palm oil as substrate. A fermentation-defoaming tandem system was developed to resolve the problems of foaming and medium overflow during scale-up. Finally, the titer of rhamnolipid reached 60 g/l and the yield reached 80 % in a 300 l fermentation-defoaming tandem system. The work reveals the potential for producing high-performance rhamnolipids from renewable resources on a large scale.

Rhamnolipid production, characterization and fermentation scale-up by Pseudomonas aeruginosa with plant oils

Construction and optimization of Escherichia coli for producing rhamnolipid biosurfactant

Graphene oxide has covalently modified by chito oligosaccharides and γ-polyglutamic acid to form GO-CO-γ-PGA, which exhibits excellent performance as a drug delivery carrier, but this carrier did not have the ability to actively target. In this study, the targeting property of breast cancer tumor cell exosomes was exploited to give GO-CO-γ-PGA the ability to target breast tumor cells (MDA-MB-231), and the drug mitoxantrone (MIT) was loaded to finally form EXO-GO-CO-γ-PGA-MIT with an encapsulation efficiency of 73.02%. The pH response of EXO-GO-CO-γ-PGA showed a maximum cumulative release rate of 56.59% (pH 5.0, 120 h) and 6.73% (pH 7.4, 120 h) for MIT at different pH conditions. In vitro cellular assays showed that EXO-GO-CO-γ-PGA-MIT was more potent in killing MDA-MB-231 cells due to its targeting ability and had a significantly higher pro-apoptotic capacity compared to GO-CO-γ-PGA-MIT. The results showed that this bionic nano-intelligent drug delivery system has good drug slow release function and it can increase the local drug concentration of tumor and enhance the pro-apoptotic ability of MIT, so this newly synthesized bionic drug delivery carriers (EXO-GO-CO-γ-PGA-MIT) has potential application in breast cancer treatment.

https://iopscience.iop.org/article/10.1088/1361-6528/ac49bf/pdf

Construction of an exosome-functionalized graphene oxide based composite bionic smart drug delivery system and its anticancer activity

Effects of shining pondweed (Potamogeton lucens) on bacterial communities in water and rhizosphere sediments in Nansi Lake, China

Rhamnolipid is an anionic surfactant which is free of toxicity and pollution, biodegradable, high in selectivity and specificity and excellent in surface activity and has unique application prospects in multiple industrial fields such as medicine, food, cosmetics and environment protection. The invention provides Pseudomonas aeruginosa TIB-R02 CGMCC No.9376 with the high rhamnolipid yield and the high conversion rate through screening. Related fermentation equipment is transformed according to the fermentation characteristic of Pseudomonas aeruginosa, and a series connection fermentation experiment of 300L fermentation tanks is realized. According to the production state of the producing strain and the characteristic of the equipment, the production process of producing rhamnolipid in a fermented mode through Pseudomonas aeruginosa TIB-R02 CGMCC No.9376 is developed, and while the rhamnolipid yield is high, the liquid leakage problem caused by surface activity brought by a great deal of rhamnolipid can be controlled. By using the equipment and the fermentation process, when palm oil with the concentration of 75 g/L serves as a carbon source, the rhamnolipid yield reaches 60.6 g/l, and the conversion rate reaches 80% or more. Therefore, the strain and the production process have good industrial application prospects.

Zhijin Gong

Papers

Rhamnolipid production, characterization and fermentation scale-up by Pseudomonas aeruginosa with plant oils

Construction and optimization of Escherichia coli for producing rhamnolipid biosurfactant

Construction of an exosome-functionalized graphene oxide based composite bionic smart drug delivery system and its anticancer activity

Effects of shining pondweed (Potamogeton lucens) on bacterial communities in water and rhizosphere sediments in Nansi Lake, China

Pseudomonas aeruginosa for producing rhamnolipid biosurfactant with palm oil and application thereof