Purification and Identification of Lipid-Lowering Protein from Barley Extract after Lactiplantibacillus plantarum dy-1 fermentation

Previous studies have found that the protein in barley extract fermented by Lactiplantibacillus plantarum dy-1 has the ability to inhibit lipid accumulation. However, the isolation, purification, and structural identification of the protein with lipid-lowering activity were still needed. In the present study, barley protein fermented by L. plantarum dy-1 with the optimal lipid-lowering ability was isolated and purified in three steps: using ammonium sulfate precipitation, anion-exchange chromatography, and size-exclusion chromatography. Combined with the model of HepG2 cells induced by oleic acid, the results showed that the pure protein LFBEP-C1 had the best lipid-lowering potential. Furthermore, our research found that LFBEP-C1 enriched the content of hydrophobic amino acids in LFBEP-C1. Ultraviolet spectroscopy analysis indicated that the glycosidic bond in LFBEP-C1 was an O-type glycosidic bond. The FTIR and circular dichroism spectra indicated that α-helix and random coil were the main secondary structures of LFBEP-C1. Mass spectrometry determined the theoretical molecular weight of LFBEP-C1 as 48 kDa, and its amino acid coverage was 63%. These findings suggest that the protein LFBEP-C1 with the best lipid-lowering activity was isolated and purified, and its structural characteristics were identified.