Iranian Journal of Medical Microbiology

Background and Aims: 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.
Materials and Methods: 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.
Results: 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.
Conclusions: 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.
 

Background and Aims: Vitamin D3 deficiency can causes many diseases such as rickets, osteopenia and osteoporosis and increases the risk of some types of cancer. Probiotic strain of Lactobacillus plantarum, which can store fat-soluble vitamin D3 in its bulk, can reduce the effects of vitamin D3 deficiency in addition to being able to produce products with probiotic benefits..
Materials and Methods: This research was carried out in 2016. By designing the one-factor-at-a- time tests, the range of possible effective variables on vitamin D3 absorption in bacterial mass and effective factors were selected. Optimization of vitamin D3 entrapment in biomass of bacteria was performed using response surface methodology via Box-Behnken design. The high-performance liquid chromatography was employed for determination of vitamin D3 quantities.
Results: Among the parameters affecting vitamin D3 entrapment, three factors including incubation temperature, initial vitamin D3 and sucrose concentrations were most effective. The optimal points were obtained at vitamin D3 concentration of 351723.537 IU/mL, sucrose concentration of 2.89 (g/L) and incubation temperature of 33.8 °C. The maximum value of vitamin D3 in dry cell weight of L. plantarum was 1028.5 IU/g which was consistent with the proposed statistical model.
Conclusions: In this study L. plantarum enriched with vitamin D3 was produced and optimized for the first time. Experimental and statistical studies confirm the accuracy and reliability of this optimization.