Enhancement of bio-desulfurization capability of a newly isolated thermophilic bacterium using starch/iron nanoparticles in a controlled system

Due to the increasing application of oil and petroleum products, increased environmental contamination has become a matter of concern. Bio-desulfurization process may be used to eliminate sulfur from fossil fuels in the moderate condition. In this study, a thermophilic bacterium was isolated that was able to desulfurize dibenzothiophene. 16S rRNA sequencing indicated that this strain is related closely to Bacillus thermoamylovorans (97%). This strain grew in Basal salt medium containing DBT (100 mgl−1) as the only sulfur source, at 55°C and showed maximum growth (OD660 = 0.850) following 72 h incubation time. 2‑hydroxybiphenyl was produced at the maximal concentration (26.13 ± 0.12 mgl−1) at 72 h. Bio-desulfurization and growth rate factors were optimized using response surface methodology. Starch/Fe3O4 and starch/Fe nanoparticles were used for enhancement of BDS efficiency. The size of starch/Fe3O4 and starch/Fe nanoparticles were 20 and 30-40 nm, respectively, as described by using scanning electron microscope and transmission electron microscope. The results showed that the immobilized cells by starch/Fe3O4 and starch/Fe nanoparticles had higher desulfurization capacity, about 10% and 22% more, respectively. Also, BDS in a bioreactor in the presence of nanoparticles was increased 25% with respect of the process occurred in the flask.