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The combustion of fossil fuels containing sulfur results in the release of sulfur dioxide into the atmosphere and environmental pollution. Hence, the researchers focused on the biological desulfurization method. Dibenzothiophene is used as the model molecule to study the ability of the desulfurization of microorganisms. The most suitable sources of carbon, nitrogen and sulfur concentration optimized by response surface method to obtain the highest cell growth and biological desulfurization activity. The performance of iron nanoparticles on the growth and biodesulfurization activity of thermophilic bacterium Bacillus thermoamylovorans strain EAMYO was investigated. Characterization of starch-modified iron nanoparticles was performed by TEM, SEM. The images of TEM and SEM of starch / Iron nanoparticles showed that the Fe₃O₄ and Fe0 nanoparticles were 20 and 30 nm, respectively. The investigating the growth of microorganism in the presence of iron nanoparticles showed that these nanoparticles not only did not have a toxic effect on microorganism growth, but also increased the growth of microorganism in 96 h (OD 660 = 1.864, 1.896 respectively in the presence of nanoparticles Fe₀ and Fe₃O₄), while the highest rate of growth in the absence of nanoparticles in 96 h (OD660 = 1.51). Also, the activity of desulfurization in the presence of starch/Fe₀ nanoparticles and starch/Fe₃O₄ / starch increased by 26.52% and 10.75%, respectively, compared to the cells without the coating of iron nanoparticles.