Abstract: ​In this thesis, microalga Dunaliella salina is highlighted as a novel source of protein to sustain the human needs. As demonstrated in this thesis, the biochemical composition of D. salina is not fixed, and can be substantially influenced by internal and external conditions. In order to comply with the human requirement of protein, various important factors affecting the protein quantity and quality of D. salina have been evaluated in this thesis for an optimized production strategy. All tested parameters, namely salinity, pH, light regimes (continuous light and light/dark cycle), light intensity, nutrient levels and growth phases can contribute to significant variations of protein content and essential amino acid (EAA) level in D. salina. Ultimately, D. salina is capable of producing high amount of superior quality protein, complying with the FAO reference for human consumption. Even better, such protein of superior quality can be accompanied by unique β-carotene accumulation in D. salina, a pigment with anti-oxidant pro-vitamin A effect. In the end, according to the techno-economic analysis (TEA), it is economically feasible to produce D. salina biomass for human nutrition.

Abstract: ​Food production is a cornerstone in contemporary industrial societies. Its production requires land, water and enormous amounts of fertilizers. These precious fertilizers enter the linear food chain and suffer from a cascade of inefficiencies, resulting in detrimental effects to the environment. A radical transforming of the current food production chain is, therefore, essential to guarantee a sustainable future for humanity. ​This thesis has studied the production of microbial protein (i.e. single-cell protein), which is the use of microorganisms such as yeast, fungi, algae and bacteria as protein ingredient for animal feed. The type of microorganisms targeted in this thesis were purple non-sulfur bacteria (PNSB). These bacteria are an extremely heterogenic group that contain photosynthetic pigments and are able to perform anoxygenic photosynthesis. The core focus of the thesis was technology development for the production of PNSB as a source of microbial protein on wastewater and fresh fertilizers. In the final stage of this research, it was the objective to explore the potential of PNSB as a nutritious feed ingredient for shrimp. ​Overall, this work has provided the building blocks to transform the conventional food production chain. The findings show that PNSB production and biomass valorization is within reach. Further pilot implementation and cost reduction will facilitate the introduction of PNSB production in future’s wastewater treatment plants and the valorization of the biomass as nutritious animal feed ingredient.​

Abstract: In order to find out whether the existing laser systems can be employed to remove superimposed layers of paint on secco wall paintings in a selective way, laser tests were carried out on three types of prepared samples simulating three stratigraphies that are frequently encountered in practice. OM, EPMA, colorimetry, mu Raman, and FT-IR were used to evaluate the results. It was found that Q-switched Nd:YAG lasers emitting at 1,064 nm could be employed to remove unwanted layers of oil paint and limewash, but the treatment of large areas requires implementation of a computer-controlled X-Y-Z station in order to control the parameters. However, the applicability of this technique will remain limited as ablation at the established optimum parameters implied a discoloration of the pigments cinnabar, yellow ochre, and burnt sienna. Moreover, it was observed that no ablation took place when the limewash thickness exceeds 25 mu m. Unwanted layers of acrylic could be removed in an efficient way with an excimer laser emitting at 193 nm.

Abstract: Aptamers are short, synthetic DNA or RNA molecules that are characterized by a specific 3D conformation which enables specific target recognition. Aptamers are promising tools in many application fields from sensing to therapeutics. One of the major challenges in the aptamer field is understanding the relationship between the sequence and what determines the higher-order structure and specific interactions with targets. Therefore, this PhD thesis focuses on the use of different mass spectrometry (MS) based approaches to characterize aptamers and their interactions. Several of these approaches are already widely applied to study other biomolecules, such as proteins, but are still largely unexplored for aptamers and oligonucleotides in general. A first focus was put on obtaining information on the higher-order structure and conformational stability of aptamers using a combination of MS and with ion mobility (IM) spectrometry by performing collision-induced unfolding (CIU) experiments. CIU was shown to hold great promise to analyze the conformational dynamics and gas-phase stabilities of aptamers. Next, the capabilities and limitations of native IM-MS for the analysis of noncovalent interactions of aptamers were demonstrated. The conformational behavior and interactions of cocaine-binding aptamers were studied and it was found that relative binding affinities of aptamers that only differ slightly in sequence and structure can be determined using native MS. Moreover, native IM-MS allowed the detection of small conformational changes upon binding of a target, which were found to be dependent on the binding mode of the aptamer. An adaptive binding mechanism was suggested for flexible aptamers that require more reorganization upon binding. In the final part of this thesis, the importance of thoroughly characterizing and validating aptamer-target interactions before using them in an application was emphasized. Moreover, the gathered insights were applied in our own development of a proof-of-concept aptamer-based sensor. This was shown by investigating the interactions of ampicillin aptamers which were found to not bind the target they were selected for in the first place. A multi-analytical approach combining complementary techniques was used for this purpose since no single technique is generally applicable to characterize all aptamers and their interactions and to obtain a comprehensive picture of the aptamer-target interactions. Furthermore, such multi-analytical approach was used to characterize a testosterone-binding aptamer while developing an aptamer-based electrochemiluminescent sensing strategy for this target. This shows the importance of native MS, in combination with other techniques, to thoroughly understand the aptamer-target interactions in the development of a designed application.