Removal of Fat from Surfaces by Lipase-Enhanced Purified Water

Growing concern over the environmental impact of conventional detergents has started the search for ecofriendly washing methods, including the use of purified water. Previous studies show that purified water facilitates the removal of olive oil from hydrophilic surfaces via roll-up and bulk mechanisms by promoting electrostatic interactions, while pH-adjusted purified water is effective on hydrophobic surfaces. Here, we investigated lipase-enhanced cleaning with purified and nonpurified water, as well as phosphate buffer solutions, for the removal of olive oil films from both hydrophobic and hydrophilic surfaces, as well as glycerol dioleate films from hydrophilic surfaces. The lipase used was a fungal lipase extracted from Rhizopus niveus. Cleaning efficiency was evaluated by gravimetric analysis and quartz crystal microbalance with dissipation (QCM-D). Both methods showed that lipase enhanced cleaning performance in purified water and buffer solution below 40 °C. Even small amounts of lipase in purified water or buffer increased washing efficiency or led to nearly complete oil removal, whereas lipase in tap water showed limited effectiveness. Contact angle and interfacial tension measurements show that the interaction between olive oil and lipase lowers surface tension by hydrolyzing triglycerides into amphiphilic free fatty acids (FFAs). These FFAs act as surfactants at the air/water interface, reducing interfacial tension and promoting oil droplet formation rather than oil spreading, thereby facilitating oil removal. Overall, lipase enables efficient cleaning under mild, surfactant-free conditions, demonstrating strong potential for the development of enzyme-based, environmentally sustainable washing systems based on purified water.