Characteristics of surface layer proteins from two new and native strains of Lactobacillus brevis

Neda Eslami, Lorestan University of Medical Sciences and Elahe Mobarak Qamsari, Alzahra University, Tehran and Rouha Kasra Kermanshahi, Alzahra University, Tehran and Mohammad Erfan, Shahid Beheshti University of Medical Sciences and Parinaz Ghadam, Alzahra University, Tehran and Soroush Sardari, Pasteur Institute of Iran (2016) Characteristics of surface layer proteins from two new and native strains of Lactobacillus brevis. International Journal of Biological Macromolecules, 95 (2017). pp. 1004-1010.

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Abstract

In this work, some important characteristics of surface layer (S-layer) proteins extracted from two new and native Lactobacillus strains, L.brevis KM3 and L.brevis KM7, were investigated. The presence of S-layer on the external surface of L.brevis KM3 was displayed by thin sectioning and negative staining. SDS-PAGE analysis were shown same dominant protein bands approximately around 48 kDa for both S-layer proteins. Moreover, the S-layer reappeared when LiCl treated cells were allowed to grow again. Protein secondary structure and thermal behavior was evaluated by using circular dichroism (CD) and differential scanning calorimetry (DSC), respectively. Both S-layer proteins had high content of β-sheet and low amount of α-helix. The thermograms of lyophilized S-layer proteins of L.brevis KM3 and L.brevis KM7 showed one transition peak at 67.9 ºC and 59.14 ºC, respectively. To determine monodispersity of extracted S-layer proteins, dynamic light scattering (DLS) was used. The results indicated that the main population of S-layer molecules in two tested lactobacillus strains were composed of monomer with expected diameter close to 10 nm. Furthermore, Zeta potential measurements were showed positive potential for both S-layer proteins, as expected. Our results could be used as the basis for biotechnological applications of these two new S-layer proteins. Keywords: Surface layer proteins, Lactobacillus brevis, Secondary structure, Thermal behavior, Monodispersity, Zeta potential

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