Investigation of Effective Factors on the Optimization of Surface Layer Protein Production in the Deinococcus radiodurans R1 Strain using Response Surface Method

Due to its self-assembly properties on variety of surfaces and creating regular functional groups, surface layer protein isolated from bacteria, has significant applications in the field of nanobiotechnology such as biosensor production, targeting drug delivery systems and tissue engineering. In this research, optimization of discontinuous culture medium compositions for the production of HPI surface layer protein from Deinococcus radiodurans R1 strain was performed using the response surface (RSM) method.
In 2016, culture medium for 16 designed experiments with fractional factorial analysis (FFA) was prepared and effective factors among six variables of the discontinuous culture medium was investigated for the production of surface layer proteins of D.radiodurans R1. Twenty experiments were then designed for the optimization of effective variables using central composite design (CCD) method. Surface protein purity was assessed using SDS-PAGE analysis and its concentration was calculated via Bradford method.
The optimized medium containing 13.36 g/L glucose, 5 g/L yeast extraction, 5 g/L tryptone, 2 g/L HEPES buffer, 0.55 MgSO4*7H2O, 0.0368 g/L MnCl2*4 H2O, was determined. Wet cellular mass was found as 16.87 g/L, which is 24% more than TGY basic medium and 74% much more than TYG culture medium including NaCl.
Results of the Bradford method demonstrated that the concentration of surface layer protein HPI isolated from D. radiodurans R1 was 5.6 mg which was more than twice of that using 1liter of basic TGY medium.