Lipid sponge phase nanostructures as carriers for enzymes

Forskningsoutput: AvhandlingDoktorsavhandling (sammanläggning)


Lipids are organic molecules vital for living organisms. They are part of cell membranes and provide an important energy reserve once they are digested by our body. They are most commonly known as fats and oils. Some important so-called polar lipids are amphiphilic molecules, which means they have a head group that is water ‘loving’ (hydrophilic) and a hydrocarbon tail is water ‘hating’ (hydrophobic) as shown in Figure 1. It is well known that oils do not mix well with water. Therefore, when polar lipid molecules are added to water they organize themselves so that the head group is in contact with water while the tail is not. This is known as lipid self-assembly and, for example, that is how cell membranes are formed, where the important part of the structure is a lipid bilayer (Figure 1).
Depending on the type of lipid used and the environmental conditions (pH, temperature, salt concentration), they can form a variety of different structures in water. This makes lipids very useful for different applications, especially in medicine and food industry, where they are commonly used as encapsulation systems. In this thesis I have used a lipid self-assembly structure called lipid sponge phase. As the name indicates, it has a resemblance to a bathtub sponge, where the sponge solid material will be the lipid network while the holes with air are filled with water. This sponge phase has a bilayer structure as in the cell membranes. However, in this case the bilayer is bent so that it forms a network of lipid bilayers and water pores (as shown in the cover). These types of structures were studied in detail with different techniques to understand how to use them as encapsulation systems.
The second part of this thesis consists of encapsulating two proteins into these lipid sponge phases. Proteins are large and complex biomolecules sensitive to degradation. Moreover, they are required for the structure, function and regulation of the body’s cells, tissues and organs. Proteins that are in charge of accelerating biochemical reactions are called enzymes. In this work the encapsulation of two enzymes used in food industry was investigated to increase their stability. Aspartic protease is an enzyme used in the cheese ripening process. Its function is to destabilize the milk and, as a result, the milk is aggregated and cheese curd is formed. An encapsulation of this enzyme could give more control over the ripening process and, hence, cheese texture and flavour could be tuned accordingly. The other enzyme studied here, β-galactosidase, is responsible for breaking down lactose and as such, it is used to produce lactose free milk and other dairy products. Encapsulation of β-galactosidase could provide a larger stability to this enzyme, but it could also make it easier to use. This is very important since nowadays an increasing fraction of the population has lactose intolerance problem, i.e. they lack this enzyme. As a consequence, the demand of β-galactosidase in food industry is rising.
The results showed that the lipid sponge phase could successfully encapsulate these two proteins and protect them from degradation. Since proteins are very large biomolecules, this was possible due to the large pores and flexibility of the sponge phase.


Enheter & grupper

Ämnesklassifikation (UKÄ) – OBLIGATORISK

  • Fysikalisk kemi


Tilldelande institution
Handledare/Biträdande handledare
Tilldelningsdatum2019 mar 15
  • Lund University, Faculty of Science, Department of Chemistry
Tryckta ISBN978-91-7422-628-7
StatusPublished - 2019 feb

Relaterad forskningsoutput

Maria Valldeperas Badell, Wiśniewska, M., Ram-On, M., Kesselman, E., Danino, D., Tommy Nylander & Barauskas, J., 2016 aug 30, I : Langmuir. 32, 34, s. 8650-8659 10 s.

Forskningsoutput: TidskriftsbidragArtikel i vetenskaplig tidskrift

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