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Celiac disease is the most common disease caused by gluten consumption and the only way to prevent it is to use gluten-free foods. The aim of this study was to optimization the formulation of gluten-free bread based on quinoa flour, laccase enzyme, and xanthan gum. For this purpose, the sensory properties and texture of bread under the influence of independent variables including quinoa flour (0-50%), xanthan gum (0-0.5%), and laccase enzyme (0-2 units of enzyme activity per gram of flour (U/g) were evaluated using the response level method based on the central composite design. Then some qualitative characteristics of gluten-free bread sample in optimal conditions were compared with the control sample (gluten-free bread containing rice and corn flours without quinoa flour, laccase enzyme, and xanthan gum) for 7 days of storage. The results showed that quinoa flour and laccase enzyme had a significant effect on sensory properties including crust color, porosity, taste, aroma, firmness, and overall acceptibility (p<0.05) of breads. While the effect of quadratic level of gum on overall acceptibility as well as the interaction of laccase enzyme and xanthan gum on bread firmness was significant (p<0.05). The optimal bread formulation consisted of 40% quinoa flour, 0.46% xanthan gum, and 2 U/g laccase enzyme. Comparison of the gluten-free optimal sample with the control gluten-free sample showed that the enthalpy and peak temperature of the control bread was higher than the optimal bread, which indicates more staleness. In terms of textural properties and sensory evaluation, the optimal sample was significantly better than the control sample. However, in terms of L* color indice, the control sample showed higher values (p<0.05).

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Introduction: Today, the biosynthesis of nanoparticles (NPs) assisted by microorganisms (particularly bacteria) received increasing attention. In this study, Bacillus subtilis strain SFTS, a bismuth-reducing bacterium, was isolated from the soil of a copper mine in the South of Iran and used for biosynthesis of bismuth NPs (Bi NPs).
Materials and methods: Bacillus subtilis strain SFTS was identified by conventional identification tests and the 16S rDNA fragment amplification method. Characterizations of the bio-fabricated Bi NPs were examined using FTIR, EDS, XRD, TEM, and SEM analysis after purification of Bi NPs. In addition, the synergistic effect of biogenic Bi NPs in combination with different antibiotics was also investigated.
Results: The attained results revealed that the biosynthesized Bi NPs average size was 22.36 nm and spherical in shape. The XRD pattern showed that the biosynthesized nanoparticles consisted only of Bi₄ and monoclinic crystals. Furthermore, the results of antibacterial effect of Bi NPs in combination with various antibiotics showed that the nanoparticles represented the highest synergistic effect together with imipenem and the lowest effect in combination with tetracycline against clinical strains of E. coli and K. pneumoniae. Significant difference between synergistic effect of Bi NPs with antibiotics compared to antibiotics disc alone against E. coli and K. pneumoniae strains was observed (P<0.001).
Conclusion: This study showed that Bi NPs biologically synthesized by Bacillus subtilis strain SFTS had a small size and different structure. However, finding about their antibacterial effect and related mechanism merit further investigations.