Sequential extraction of protein, melanin and cellulose from Zanthoxylum bungeanum seeds and their structural characterization

Abstract

Zanthoxylum bungeanum seeds (ZBS) are rich in proteins, melanin, and cellulose. However, as a byproduct of the Zanthoxylum bungeanum processing industry, they are usually directly discarded by manufacturers, resulting in a significant waste of natural resources. In this study, a continuous extraction method was used to extract proteins, melanin, and cellulose from ZBS. The results showed that the extraction rate of protein was 61.02 %, whereas the yields of melanin and cellulose were 2.61 % and 11.73 %, respectively. Amino acid analysis revealed that the ZBS protein contains a high proportion of hydrophobic amino acids. The SDS-PAGE results showed that the ZBS protein was mainly composed of three subunits, indicating that it was mainly composed of polypeptide chains with different molecular weights. Elemental analysis showed that ZBS melanin contained 52.1 % C, 5.17 % H, 6.27 % N, and 0.65 % S. Electronic paramagnetic resonance spectroscopy revealed resonance absorption consisting of a single symmetrical line without hyperfine division, which is consistent with the characteristics of melanin. Fourier transform infrared spectroscopy and X-ray diffraction results indicated that ZBS cellulose was consistent with the characteristics of cellulose type I crystals. These results indicate that the continuous extraction method introduced in this study can improve the utilization value of ZBS.

Keywords: Melanin; Protein; Zanthoxylum bungeanum seeds.