Extraction Separation of Rhamnolipids by n ‐Hexane via Forming Reverse Micelles

Glycolipid Biosurfactant Production from Waste Cooking Oils by Yeast: Review of Substrates, Producers and Products

Biosurfactants are a microbially synthesized alternative to synthetic surfactants, one of the most important bulk chemicals. Some yeast species are proven to be exceptional biosurfactant producers, while others are emerging producers. A set of factors affects the type, amount, and properties of the biosurfactant produced, as well as the environmental impact and costs of biosurfactant’s production. Exploring waste cooking oil as a substrate for biosurfactants’ production serves as an effective cost-cutting strategy, yet it has some limitations. This review explores the existing knowledge on utilizing waste cooking oil as a feedstock to produce glycolipid biosurfactants by yeast. The review focuses specifically on the differences created by using raw cooking oil or waste cooking oil as the substrate on the ability of various yeast species to synthesize sophorolipids, rhamnolipids, mannosylerythritol lipids, and other glycolipids and the substrate’s impact on the composition, properties, and limitations in the application of biosurfactants.

Recent progress and trends in the analysis and identification of rhamnolipids

Rhamnolipids have extensive potential applications and are the most promising biosurfactants for commercialization. The efficient and accurate identification and analysis of these are important to their production, application and commercialization. Accordingly, significant efforts have been made to identify and analyse rhamnolipids during screening of producing strains, fermentation and application processes. Cationic cetyltrimethylammonium bromide-methylene blue (CTAB-MB) test combines a series of indirect assays to efficiently assist in the primary screening of rhamnolipids-producing strains, while the secretion of rhamnolipids by these strains can be identified through TLC, FTIR, NMR, electrospray ionization mass spectrometry (ESI-MS) and HPLC-MS analysis. Rhamnolipids can be quantified by colorimetric methods requiring the use of concentrated acid, and this approach has the advantages of reliability, simplicity, low-cost and excellent reproducibility with very low technological requirements. HPLC-MS can also be employed as required as a more accurate quantification method. In addition, HPLC-ELSD has been established as the internationally acceptable measure of rhamnolipids for commercial purposes. The preparation of well-accepted rhamnolipids standards and modifications of analysis operations are essential to further enhance the accuracy and improve the simplicity of rhamnolipid analysis.Key points• Current status of R&D works on determination of rhamnolipids is listed• Advantages and disadvantages of various types analysis are summarized• Limitations of current rhamnolipid quantification are discussed Graphical abstract.