Journal of Surfactants and Detergents最新文献

Rhamnolipids, simply divided into mono-rhamnolipids and di-rhamnolipids, their physicochemical properties are structure-dependent. This study explored to increase the proportion of di-rhamnolipids biosynthesized from Pseudomonas aeruginosa and evaluate the relationship between activity and di-rhamnolipids proportions. P. aeruginosa SGrhlC was constructed by increasing the rhlC gene in P. aeruginosa SG. HPLC-MS results indicated that SGrhlC produced more di-rhamnolipids (62.32%) than that of the wild-type strain SG (45.24%). Both the species and proportion of di-rhamnolipids were increased, mainly Rha-Rha-C₈-C₁₀ and Rha-Rha-C₁₀-C₁₀. The rhamnolipids produced by SGrhlC was thermostable and salt-tolerant. The SGrhlC rhamnolipids decreased surface tension of water to 27.0 mN/m with a critical micelle concentration (CMC) of 50 mg/L and emulsified crude oil with an emulsification index of 66.9 ± 1.5%. The SGrhlC rhamnolipids exhibited antimicrobial activity against Staphylococcus aureus and Cladosporium sp. with IC50 (half maximal inhibitory concentration) values less than 15 mg/L, and washed 73.02% ± 1.77% of oil from petroleum-contaminated soil. Physicochemical activities of three bacterial rhamnolipids varied with their di-rhamnolipids proportions. Results indicated that the higher proportions of di-rhamnolipids were, the lower CMC, better surface activity and higher washing oil rate were, while the weaker emulsifying activity and lower antimicrobial activity were. The SGrhlC rhamnolipids showed better surface activity and a lower critical micelle concentration, which was superior for wetting, foaming, desorbing and dispersing. This study revealed that P. aeruginosa can be genetically regulated to biosynthesize rhamnolipids with specific structure. Perspectives of the customized biosynthesis and applications of rhamnolipids were also discussed.

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.

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.