Journal of Surfactants and Detergents

doi: 10.1002/jsde.12688pmid: N/A

Hayes, Douglas G.; Ashby, Richard D.; Ju, Lu‐Kwang; Smith, George A.

doi: 10.1002/jsde.12795pmid: N/A

Münßinger, Sini; Beck, Alexander; Oraby, Amira; Zibek, Susanne

doi: 10.1002/jsde.12764pmid: N/A

The glycolipids cellobiose lipids (CL) and mannosylerythritol lipids (MEL) are biosurfactants mainly synthesized by microorganisms of the Ustilaginaceae family. They have a large structural diversity, varying in their sugar moieties and the attached fatty acids, resulting in a prospectively broad range of applications. This literature review provides a detailed overview of known microbial producers of CL and MEL, and their respective metabolic pathways that result in different molecular structures. Further, current advances in the aerobic fermentative synthesis of the glycolipids and their purification methods are illustrated. All influencing factors identified to date with regard to the fermentation are highlighted in detail: For CL synthesis usually hydrophilic carbon sources are used as substrate, whereas hydrophobic carbon sources are usually metabolized to MEL. Nitrogen limitation was described as a major trigger for glycolipid synthesis and an acidic pH range was favored for increased CL production. An overview of applied fermentation parameters in recent publications (e.g., substrate‐concentrations, feeding approaches) demonstrates the future potential of CL and MEL production optimization. Foaming during fermentation is either combated or exploited by foam fractionation as the first purification step. The current purification processes focus on solvent extractions and chromatography in the laboratory scale and a need for development was identified for future scale‐up. Finally, environmental hotspots during CL and MEL production are presented and future optimization potentials are highlighted.

Zulkifli, Wan Nur Fatihah Wan Muhammad; Hayes, Douglas G.; Maurad, Zulina Abdul; Zan, Arniza Mohd

doi: 10.1002/jsde.12725pmid: N/A

Mannosylerythritol lipid (MEL) is a microbial surface‐active glycolipid biosurfactant produced by numerous microorganisms. MEL is produced as a major product by Pseudozyma sp. and as a minor product by Ustilago sp. MEL has recently received much practical attention due to its structural diversity, broad biochemical functions, and biocompatibility with the environment. In this review, the production of MEL from various feedstocks, and antimicrobial and antiadhesive properties are discussed. Furthermore, the applications of MEL as an antimicrobial agent in food, moisturizer in cosmetics, as an apoptotic agent in pharmaceuticals, and as a wetting agent in agriculture applications are highlighted. Finally, an overview of MEL production from waste materials presents huge potential for increasing the necessary change to a circular economy.

Ishizaki, Ryu; Araki, Michiaki; Quan, Glen Lelyn; Hirata, Yoshihiko

doi: 10.1002/jsde.12779pmid: N/A

Waste frying oil (WFO) is a degraded form of oil that is produced from repeated exposure to high temperatures during cooking. Many research studies have focused on the use of recycled WFO. These studies are highly promoted because of the need to find new ways of reducing the negative impact of WFO on the environment. One of these studies focused on the production of sophorolipid (SL), a naturally derived eco‐friendly glycolipid biosurfactant. Unfortunately, the environmental and societal advantages brought about by the wide‐spread use of SL are offset by its high production cost. WFO is a high‐volume, inexpensive material that can be used as a substrate for SL production. As such, by utilizing WFO as a feedstock material cost reduction can be realized to improve large‐scale application potential. One drawback to the use of WFO is that its physical characteristics are different from fresh oil and its effect on SL productivity (g/day) has not been investigated. This research focused on the effect of acid value (AV), peroxide value (PV), and carbonyl value (CV) of WFO on SL productivity. It was confirmed that SL titers (111.1 vs. 106.7 g/L) did not differ significantly after using either fresh oil (CV <0.01) or WFO, respectively. In addition, this research also confirmed that higher WFO degradation required longer culture periods (from 6 days to 9 days) to reach comparable SL concentrations as that produced with fresh oil.

Santos, Olga Silva; Lima, Frederico Alves; Cardoso, Vicelma Luiz; Resende, Miriam Maria

doi: 10.1002/jsde.12747pmid: N/A

This research studied the wastewater chromium removal efficiency by dissolved air flotation (DAF) using a rhamnolipid (RL) biosurfactant as a collector. An experimental flotation DAF apparatus with 6 vessels of 2 L containing a coupled saturator injecting compressed air at 5.88 kPa in the vessels was used. The total RL concentration of the broth resulting from fermentation was 9 ± 1.0 g/L. This broth was used in nature in the DAF experiments. A central composite design (CCD) was used to optimize removal of Cr(VI) and total Cr with regards to two independent variables, pH (3.17–8.83) and iron concentration of the medium (0–225.0 mg/L), with a three assays performed at the conditions of the central point of the design. The experimental conditions for DAF were an initial hexavalent Cr concentration of 100 mg/L; RL broth volume of 500 mL; saturated with oxygen water volume of 200 mL; and a rapid mixing time of 6 min through stirring at 120 rpm. The results showed that under acidic pH conditions and with high iron concentrations, both the Cr(VI) and total Cr removal rates were highest. The optimal removal region determination was at a pH of 3.5 and iron concentration of 180 mg/L. Subsequently, cationic tannin‐based flocculant was also evaluated as a collector, and ferrous sulfate was used as a coagulant during Cr(III) removal. The best Cr(III) removal percentage was obtained at cationic polymer concentrations of 300 mg/L with Cr(III) removal of 50.8% and a pH of 5.5.

Yu, Fei; Yang, Qining; Cui, Tianyou; Luo, Li; Zhao, Mengqian; Long, Xuwei

doi: 10.1002/jsde.12738pmid: N/A

Mannosylerythritol lipids (MELs), a glycolipid biosurfactant, possess great potential in many high‐value‐added fields. However, its water‐insolubility is an important obstacle to its wide application, especially in home and personal care fields. In this study, a new strategy “killing two birds with one stone” based on the chemical modification of natural MELs was developed for the preparation of hydrophilic MELs. These newly prepared MELs can be efficiently isolated from the reacted solution via stepwise extraction with a methanol/n‐hexane system. 88% of hydrophilic MELs were recovered from natural MELs, with a corresponding yield of 50%. This is mainly attributed to the esterification of fatty acids, representing the main and relatively‐difficult‐to‐remove impurities in fermentative‐produced MELs, facilitating separation from the MEL product via extraction. Moreover, these new MELs presented comparable surface activities to natural MELs while exhibiting enhanced water solubility and biocompatibility. This originates from the generation of MEL‐D, resulting from the deacetylation of natural MELs and the formation of new hydrophilic MELs containing just one hydrophobic chain (named “MEL‐G”). Hence, the present strategy is not only beneficial for the removal of impurities (fatty acids) but also for the preparation of MELs with improved hydrophilicity.

Kegel, Laurel L.; Wang, Yu‐Cheng; Szabó, Lajos Z.; Polt, Robin; Pemberton, Jeanne E.

doi: 10.1002/jsde.12746pmid: N/A

The lyotropic properties of alkyl thioglycosides with varying sugar headgroup (lactose, cellobiose, maltose, galactose, or glucose) and alkyl chain length (octyl, decyl, or dodecyl chains) are investigated by surface tensiometry, visual observation, and fluorescence spectroscopy. The results substantiate that the glycosidic S‐linkage confers considerably different solution aggregation behavior on these surfactants relative to their O‐linked counterparts, where the properties of the latter are known. The materials properties of the aggregated structures from the alkyl thioglycosides vary considerably. Micelles are formed by octyl thiocellobioside and all alkyl thiomaltosides. Turbid aggregate solutions are formed by the alkyl thioglucosides and octyl thiogalactoside, whereas the longer chain alkyl thiogalactosides are minimally soluble. Fluorescence spectroscopy of these systems confirms their aggregation in lamellar‐like structures. The alkyl thiocellobiosides and alkyl thiolactosides form hydrogels from these low‐molecular weight materials at concentrations almost an order of magnitude lower than gels using other low‐molecular weight materials. Here, hydrogels form at concentrations <0.3 wt% with some forming hydrogels at concentrations as low as 0.03 wt% from alkyl thiocellobiosides and thiolactosides, with hydrogel properties differing significantly with this slight change in the sugar headgroup. Alkyl thiocellobiosides form a nanofiber network and alkyl thiolactosides form globular hydrogels. Overall, these results clearly document materials properties that can readily be controlled and designed depending on molecular structure.

Chirac, Marie‐Françoise; Cambos, Sophie; Guilbot, Jérôme; Nawrocki, Corinne; Marchand, Régis; Roso, Alicia

doi: 10.1002/jsde.12752pmid: N/A

Alkyl polyglycosides (APGs), based on renewable glucose and fatty alcohols, are recognized for their performance and biodegradability. Hydrotropic/solubilizing effect properties have already been identified on short‐chain variants such as hexyl and ethylhexyl, but these ingredients were not fully bio‐based. This study investigated the hydrotropic/solubilizing properties of eco‐designed 100% bio‐based heptyl glucoside, under various conditions, compared to industrial and personal care benchmarks and other short chain APGs. Foaming power was firstly evaluated at different temperatures with two static methods. Hydrotropic performance was assessed with a commonly used surfactant in the presence of high electrolyte, acid and alkali concentrations. Further trials were done using ethoxylated rapeseed oil as an oil lubricant model in electrolyte‐charged aqueous solution. The solubilizing effect of hydrophobic additives such as fragrances, essential oils and vitamin E was quantified. Finally, effects on formulation preservation were screened with two natural personal care preservatives. Heptyl glucoside was found to be an effective and versatile hydrotrope for industrial applications, with additional intrinsic lubrication properties. It was also revealed as an efficient solubilizer for personal care products with the additional benefit of reducing the preservative dosage required in natural formulations. Its unusual non‐foaming nature, while not disrupting the foaming capacity of surfactants, makes it suitable for all types of cleansers. The calculated carbon footprint has a low value, making heptyl glucoside a valuable ingredient combining both performance and low environmental impact.

McMillan, Janet R.; Miller, Daniel S.; Nimako‐Boateng, Caroline; Wilson, Lauren; Kuo, Tzu‐Chi; Tesoldi, Micol Frederica; Young, Timothy; Izmitli, Aslin

doi: 10.1002/jsde.12777pmid: N/A

There is growing global demand to transition to more sustainable surfactant technologies. Towards this vision, bio‐based surfactants and biosurfactants are being explored as alternatives to traditional petrochemical surfactants. However, the transition towards these technologies is expected to be gradual, therefore there is a critical need to formulate new biosurfactants in combination with traditional surfactant classes such as alkoxylates, sulfates and amine‐oxides to achieve a balance of performance, cost, and sustainability. To this end, we report a study of the impact of sophorolipid biosurfactants on the cloud point of alcohol ethoxylates, and on the surface tension and foaming of alkyl sulfate/amine‐oxide mixtures. We make the surprising finding that high‐acid sophorolipids can act as highly efficient hydrotropes and increase the cloud point of alcohol ethoxylates. In sulfate/amine‐oxide mixtures, models of experimental data suggest that both high‐acid and high‐lactone sophorolipids can replace 40–50% of the primary surfactants without significant changes to the surface tension or foaming performance. These findings will enable the next‐generation of high performing sustainable cleaning formulations to be realized.