Identification and physicochemical properties of Lactobacillus surface layer proteins

• 1、School of Food Science and Technology, Jiangnan University, JiangSu WuXi 214122

Abstract：[Objective] The aim of this study is to screen and identify lactobacilli carrying surface layer (S-layer) proteins and characterize their physicochemical properties. Then the research on the S-layer proteins will be richer and the biochemical study methods will be built. [Methods] The S-layer proteins were extracted by lithium chloride, purified by ion exchange chromatography and identified by SDS-PAGE. The amino acid composition was analyzed with a high performance liquid chromatography for amino acid. The secondary structure was determined by the circular dichroism spectrometer. The thermal denaturation temperature was detected by the differential scanning calorimetry. [Results] The SDS-PAGE analysis showed that L. acidophilus NCFM 、L. acidophilus 11、L. gasseri 2-2 and L. casei zhang had S-layer proteins. Four S-layer proteins had high content of hydrophobic amino acids, approximate content of aspartic acid and lysine, and low content of sulphur-containing amino acids. The α-helix percent of secondary structures was higher than the β-sheet percent. The thermal denaturation temperature ranged from 59 C to 70 C, presenting low thermal stability. [Conclusion] The methods of SDS-PAGE analysis and chromatographic purification are valid identification of Lactobacillus S-layer protein. This research suggested that the composition and structure of Lactobacillus S-layer protein could affect the thermal denaturation property.

Keywords： Lactobacillus Surface layer protein Amino acid composition Secondary structure Thermal denaturation temperature