Characterization and identification of sugar beet leaves proteins and effect of high-pressure extraction in protein profiles

Date

2023-7-19

Author

Göktayoğlu, Ece

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The interest in plant-based proteins has increased considerably nowadays. Production of alternative protein sources from plants is continuously explored. Sugar beet leaves have the potential to satisfy that demand due to their high protein content with an average of 20% crude protein on dry matter basis. They are considered as agricultural waste and utilizing them as protein sources can bring them back into the food chain. Protein extraction can be performed with many different precipitation methods. Moreover, extraction efficiency can be increased by using different pretreatments. RuBisCo stands as the highest detected protein in sugar beet leaves. In this study, the extraction of RubisCo proteins from sugar beet leaves have been carried out using three different precipitation methods: isoelectric point precipitation, heat coagulation, and ammonium sulfate precipitation. In addition, effect of high-pressure homogenization on the extraction yield of protein was also investigated. High pressure-assisted extraction was conducted at 1440 bar for 2 passes. Following the extraction, proteins were freeze dried and characterized. Kjeldahl method was used to measure the total protein content and the Lowry method was used to measure soluble protein content. Structural changes were monitored by Fourier Transform Infrared (FTIR) spectroscopy. For comprehensive protein characterization, a Mass Spectrometry-based proteomic approach was followed. The Kjeldahl method found the overall protein percentages for ISO, HC, AS, ISOHP, and HCHP were %64, %66, %74, %76, and %75, respectively. Through mass spectrometry-based proteomics total of 817 proteins were found with all methods combined. 764, 763, 733, 752, and 760 proteins yieldedat ISO, HC, AS, ISOHP, and HCHP, respectively. RuBisCo, the most abundant protein, exhibited similar intensity levels across all conditions. The RuBisCo content was 29.91%, 16.65%, 35.81%, 27.60%, and 26.17%, respectively, in ISO, HC, AS, ISOHP, and HCHP. Cluster analysis indicated that, high-pressure assisted techniques showed elevated levels of proteins predominantly.

Subject Keywords

Sugar beet leaves, Protein extraction, Alternative plant-based protein source, RuBisCo protein, Mass Spectrometry-based proteomic analysis

URI

https://hdl.handle.net/11511/104535

Collections

Graduate School of Natural and Applied Sciences, Thesis