Special Issue: Glycolipid biosurfactants: Synthesis, properties, and applications

The following Special Issue highlights the current state-of-the-art for the research and development (R&D) of glycolipid biosurfactants, including sophorolipids, rhamnolipids, mannosylerythritol lipids, and others. Glycolipids have generated great interest in recent years due to many desirable properties: possessing good surface activity and antimicrobial activity, fully biobased, biocompatible, nonecotoxic, and biodegradable, to name a few. According to SciFinder-n® (American Chemical Society, Columbus, OH, USA), the number of hits focusing upon "biosurfactants" (including papers in scientific journals, book chapters, and patents) has increased linearly between 2000 and 2021, from 74 papers to 957 papers. Similarly, the number of hits for sophorolipids has increased linearly from 24 in 2007 to 246 in 2023, and for rhamnolipids, from 35 hits in 2002 to 497 in 2021. Of these, 108, 16, and 38 papers have been published on "biosurfactants," "sophorolipids," and "rhamnolipids," respectively, in the Journal of Surfactants and Detergents. The production of biosurfactants is significantly large and is growing. According to a recent market report, the global biosurfactants market was valued at USD 4.41 billion in 2023 and is projected to reach USD 6.71 billion by 2032 (compound annual growth rate of 5.4%), with glycolipids (sophorolipids, rhamnolipids, and trehalose lipids) being the major contributors (Fortune Business Insights, 2024). According to the market report, the major market sectors for which biosurfactants are employed include household cleaners (amounting to ~50% of the market), followed by personal care (~25%), industrial cleaners (~10%), and others (e.g., petroleum: for enhanced oil recovery, agrochemicals, and food processing) (Fortune Business Insights, 2024). Hindering glycolipids' widespread use is their high production costs relative to other surfactants. The grand challenge has been addressed through innovations in strain engineering to improve yield and selectivity, the use of low-cost carbon-energy sources such as crude glycerol, waste cooking oil, and recently food waste, and improved downstream purification, including the development of reactive separations. Additional targets for biosurfactant R&D are to improve performance, availability, and registration, which will lead to new application areas for glycolipids, especially in niche markets. To address the improved performance, covalent modification approaches have been developed, for instance, the hydrolysis of lactonic sophorolipids to produce acidic sophorolipids. The articles in the Special Issue cover several different glycolipid types and their fermentative preparation, properties (including antimicrobial activity and self-assembly), and new application areas, such as environmental remediation and cosmetics. We, the Guest Editors, hope the reader finds the Special Issue to be a valuable resource. We are indebted to the authors preparing their outstanding articles. The authors have nothing to declare.