Structures and physicochemical characterization of enzyme extracted oil bodies from rice bran

Abstract Oil bodies (OBs) are a natural delivery system rich in functional ingredients. This study analyzed the structures, physical properties and chemical compositions of rice bran oil bodies (RBOBs) extracted by three different enzymes (Plant exacted enzyme-RBOBP, Xylanase-RBOBX, and their mixture-RBOBM), respectively. The particle size distribution and zeta-potential of RBOBs were determined. The structure of RBOBs was observed by using Cryo-scanning electron microscopy (Cryo-SEM) and confocal laser scanning microscopy (CLSM). RBOBs were also characterized by acrylamide electrophoresis (SDS-PAGE) and liquid chromatography-tandem mass spectrometry (LC-MS/MS) for protein identification. The fatty acid compositions of RBOBs were analyzed by UPLC-Q-Exactive Orbitrap/MS. The three RBOBs exhibited polydispersed size distributions. The RBOBM showed the most uniform distribution due to the highest protein content and strongest steric hindrance. X-ray diffraction (XRD) patterns showed that RBOBs were amorphous structure. SDS-PAGE proved that RBOB surface contained OB related proteins and a large number of extraneous proteins. In addition to the previously known oleosin, some new proteins (germin-like protein 16, osmotin, Histone H4, putative, expressed protein, calmodulin, putative glycopeptide et al.) were identified. The fatty acid composition of RBOB was similar to that of rice bran oil. It was useful to study the natural plant OB delivery system.