This master thesis explored washing with water grades and lipase as environmentally friendly alternatives to conventional detergents containing surfactants. On hydrophilic surfaces, purified water can remove fat through roll-up mechanism, initiated by electrostatic repulsion forces. On hydrophobic surfaces, purified water alone cannot remove fat as there are no electrostatic repulsion forces. However, addition of lipase might promote degreasing through solubilization. Lipases are only activated when encountering an oil-water interface. Once activated, lipases can hydrolyze carboxylic ester bonds in fats. The aim of this project was to evaluate if addition of lipase from Rhizopus niveus (RNL) to water grades (such as ultrapure water, DIRO, and tap water) can enhance their cleaning efficiency to remove fat-based stains from hydrophilic and hydrophobic surfaces. An interesting phenomenon was observed in contact angle measurements. On hydrophilic surface, some solutions with high RNL concentration caused the oil droplet to divide into several droplets. The involved mechanisms are yet unknown. Gravimetric analysis showed a significant increase in cleaning efficiency in most samples (except tap water) after addition of RNL. Also, the effect of interfacial changes became significant. Multiple cycle washing, with repeated interfacial changes and high rate of fat removal, was more efficient than single cycle washing. In the quartz crystal microbalance with dissipation (QCM-D) measurements, RNL had a significant effect on the frequency and dissipation data. Observed changes when washing with RNL, suggest that apart from the cleaning promoted by interfacial changes, also enzymatic cleaning was occurring. Unfortunately, the calculated cleaning efficiencies reveal that addition of RNL did not increase the cleaning efficiency in this specific washing test. To obtain extensive understanding of RNL’s behavior and activity in water grades, as well as the effect of RNL on different surfaces (without or with fats involved), further experiments are necessary.
| Identifer | oai:union.ndltd.org:UPSALLA1/oai:DiVA.org:mau-68246 |
| Date | January 2024 |
| Creators | Kokrehel, Dorina |
| Publisher | Malmö universitet, Institutionen för biomedicinsk vetenskap (BMV) |
| Source Sets | DiVA Archive at Upsalla University |
| Language | English |
| Detected Language | English |
| Type | Student thesis, info:eu-repo/semantics/bachelorThesis, text |
| Format | application/pdf |
| Rights | info:eu-repo/semantics/openAccess |
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