Background: Flagellin of Salmonella enterica serovar Enteritidis (SEF) stimulates
immune responses to both itself and coapplied antigens. It is therefore used in vaccine development
and immunotherapy. Removal of pathogenic S. enterica ser. Enteritidis from SEF production
process is advantageous due to the process safety improvement. The protein solubility analysis
using SDS-PAGE indicated that 53.49% of SEF expressed in Escherichia coli formed inclusion
bodies. However, the protein recovery from inclusion bodies requires a complex process with a low
Objective: We thus aim to study possibility of enhancing SEF expression in E. coli in soluble form
using chemical and molecular chaperones.
Methods: Chemical chaperones including arginine, sorbitol, trehalose, sodium chloride and benzyl
alcohol were used as cultivation medium additives during SEF expression. SEF solubilization by
coexpression of molecular chaperones DnaK, DnaJ, and GrpE was also investigated.
Results: All of the chemical chaperones were effective in improving SEF solubility. However,
sorbitol showed the most profound effect. SEF solubilization by molecular chaperones was slightly
better than that using sorbitol and this approach enhanced noticeably SEF soluble concentration and
SEF solubility percentage to almost two folds and 96.37% respectively. Results of limited
proteolysis assay and native PAGE indicated similar conformational states and proper folding for
SEF obtained without using chaperones and for those obtained using sorbitol and the molecular
chaperones. However, the molecular chaperones based system was less costly than the sorbitol
Conclusion: The coexpression of molecular chaperones was then considered as the most
appropriate approach for soluble SEF production. Therefore, SEF production for medical purposes
is expected to be facilitated.