Izolacija i karakterizacija Cr(VI) tolerantnih zemljišnih bakterija

In  this  study,  tolerance  of  soil  bacteria  to  hexavalent  chromium  (Cr(VI))  was  investigated.  First,  influence  of  high chromium levels of anthropogenic and geogenic origin on the  soil cultivable  bacterial community was examined. Next, a number  of  bacterial  strains  with  high  Cr(VI)  tolerance  were  isolated  from  diverse   environmental  samples  such  as  soil, sediment, water and waste material.  Strains were  identified  and  tested for  the  level of  Cr(VI) tolerance  and  the  ability to reduce toxic Cr(VI) to more innocuous Cr(III). Selected  Bacillus cereus  group strains  were further characterized  -  their morphological  and  biochemical  characteristics,  16S  rRNA  and  pycA  gene  sequences,  biofilm  formation  potential  and resistance to other heavy metals were determined. Also, more detailed study of their tolerance level and  Cr(VI) reduction was  conducted.  Strain  with  the highest  resistance  together  with the  control  chromate  sensitive  strain  were  analyzed  by STEM EDS for their cellular and endospore Cr content under different conditions. Results indicate Cr(VI) tolerant bacteria are  present  both  in  low  and  high  Cr  environments.  Majority  of  isolates  belonged  to  the  B.  cereus  group  indicating  its overall high tolerance to  Cr(VI). Certain strains exhibited high  tolerance and reduction  ability,  indicating their possible usefulness  in practical  bioremediation  application.  STEM  EDS  analysis  of  Cr(VI)-sensitive  B.  subtilis  PY79  strain  and Cr(VI)-resistant  B. cereus  group strain  NCr1a revealed  significant differences in their response to Cr(VI)  and in  their  Cr cellular and endospore content.U ovom radu ispitana je tolerantnost  zemljišnih  bakterija na šestovalentni hrom (Cr(VI)). Prvo, ispitan je uticaj visokog nivoa  hroma  antropogenog  i  geogenog  porekla  na  kultivabilnu  bakterijsku  zajednicu  zemljišta.  Dalje,  izolovani  su bakterijski sojevi sa visokom tolerancijom na Cr(VI) iz različitih sredinskih uzoraka   kao što su zemljište, sediment, voda i otpadni materijal. Sojevi su identifikovani i određen je nivo njihove Cr(VI) tolerancije i sposobnost redukcije toksičnog Cr(VI)  u  manje  toksični  Cr(III).  Odabrani  sojevi  Bacillus  cereus  grupe  su  dalje  karakterisani  –  određene  su  njihove morfološke i biohemijske karakteristike, 16S rDNK i  pycA  sekvence, potencijal formiranja biofilma i otpornost na druge teške  metale.  Takođe,  sprovedeno  je  detaljnije  ispitivanje  njihove  tolerancije  i  redukcije  Cr(VI).  Soj  sa  najvišom otpornošću  je  uporedo  sa  kontrolnim  osetljivim  sojem  analiziran  pomoću  STEM  EDS  na  sadržaj  hroma  u  ćelijama  I endosporama u različitim uslovima. Rezultati ukazuju da su bakterije tolerantne na Cr(VI) prisutne i u sredinama sa niskim i  sa  visokim  koncentracijama  hroma.  Većina  izolata  pripadala  je  B.  cereus  grupi  što  ukazuje  na njenu  uopšteno  visoku otpornost na Cr(VI). Pojedini sojevi su pokazali visoku otpornost i sposobnost  redukcije Cr(VI), što ukazuje na mogućnost njihove praktične primene u bioremedijaciji. STEM EDS analiza osetljivog B. subtilis PY79 soja i Cr(VI)- rezistentnog soja B.  cereus  grupe  NCr1a  otkrila  je  značajne  razlike  u  njihovom  odgovoru na  Cr(VI)  i  sadržaju  Cr  u njihovim  ćelijama  i endosporama

Izolacija i karakterizacija Cr(VI) tolerantnih zemljišnih bakterija

In  this  study,  tolerance  of  soil  bacteria  to  hexavalent  chromium  (Cr(VI))  was  investigated.  First,  influence  of  high chromium levels of anthropogenic and geogenic origin on the  soil cultivable  bacterial community was examined. Next, a number  of  bacterial  strains  with  high  Cr(VI)  tolerance  were  isolated  from  diverse   environmental  samples  such  as  soil, sediment, water and waste material.  Strains were  identified  and  tested for  the  level of  Cr(VI) tolerance  and  the  ability to reduce toxic Cr(VI) to more innocuous Cr(III). Selected  Bacillus cereus  group strains  were further characterized  -  their morphological  and  biochemical  characteristics,  16S  rRNA  and  pycA  gene  sequences,  biofilm  formation  potential  and resistance to other heavy metals were determined. Also, more detailed study of their tolerance level and  Cr(VI) reduction was  conducted.  Strain  with  the highest  resistance  together  with the  control  chromate  sensitive  strain  were  analyzed  by STEM EDS for their cellular and endospore Cr content under different conditions. Results indicate Cr(VI) tolerant bacteria are  present  both  in  low  and  high  Cr  environments.  Majority  of  isolates  belonged  to  the  B.  cereus  group  indicating  its overall high tolerance to  Cr(VI). Certain strains exhibited high  tolerance and reduction  ability,  indicating their possible usefulness  in practical  bioremediation  application.  STEM  EDS  analysis  of  Cr(VI)-sensitive  B.  subtilis  PY79  strain  and Cr(VI)-resistant  B. cereus  group strain  NCr1a revealed  significant differences in their response to Cr(VI)  and in  their  Cr cellular and endospore content.U ovom radu ispitana je tolerantnost  zemljišnih  bakterija na šestovalentni hrom (Cr(VI)). Prvo, ispitan je uticaj visokog nivoa  hroma  antropogenog  i  geogenog  porekla  na  kultivabilnu  bakterijsku  zajednicu  zemljišta.  Dalje,  izolovani  su bakterijski sojevi sa visokom tolerancijom na Cr(VI) iz različitih sredinskih uzoraka   kao što su zemljište, sediment, voda i otpadni materijal. Sojevi su identifikovani i određen je nivo njihove Cr(VI) tolerancije i sposobnost redukcije toksičnog Cr(VI)  u  manje  toksični  Cr(III).  Odabrani  sojevi  Bacillus  cereus  grupe  su  dalje  karakterisani  –  određene  su  njihove morfološke i biohemijske karakteristike, 16S rDNK i  pycA  sekvence, potencijal formiranja biofilma i otpornost na druge teške  metale.  Takođe,  sprovedeno  je  detaljnije  ispitivanje  njihove  tolerancije  i  redukcije  Cr(VI).  Soj  sa  najvišom otpornošću  je  uporedo  sa  kontrolnim  osetljivim  sojem  analiziran  pomoću  STEM  EDS  na  sadržaj  hroma  u  ćelijama  I endosporama u različitim uslovima. Rezultati ukazuju da su bakterije tolerantne na Cr(VI) prisutne i u sredinama sa niskim i  sa  visokim  koncentracijama  hroma.  Većina  izolata  pripadala  je  B.  cereus  grupi  što  ukazuje  na njenu  uopšteno  visoku otpornost na Cr(VI). Pojedini sojevi su pokazali visoku otpornost i sposobnost  redukcije Cr(VI), što ukazuje na mogućnost njihove praktične primene u bioremedijaciji. STEM EDS analiza osetljivog B. subtilis PY79 soja i Cr(VI)- rezistentnog soja B.  cereus  grupe  NCr1a  otkrila  je  značajne  razlike  u  njihovom  odgovoru na  Cr(VI)  i  sadržaju  Cr  u njihovim  ćelijama  i endosporama

Reusable Fe₂O₃/TiO₂/PVC Photocatalysts for the Removal of Methylene Blue in the Presence of Simulated Solar Radiation

Currently, environmental pollution by various organic pollutants (e.g., organic dyes) is a serious, emerging global issue. The aqueous environment is highly exposed to the harmful effects of these organic compounds. Furthermore, the commonly applied conventional purification techniques are not sufficient enough. Heterogeneous photocatalysis and the photo-Fenton process are effective, low-cost and green alternatives for the removal of organic pollutants. In this study, different iron(III) oxide/titanium(IV) oxide/polyvinyl chloride (Fe2O3/TiO2/PVC) nanocomposites in tablet form were investigated in the photodegradation of methylene blue (MB) under simulated sunlight, and their possible antibacterial effects were examined. The newly synthesized nanocomposites were characterized by scanning electron microscope, X-ray diffraction, UV–Vis diffuse reflectance spectroscopy, and Raman spectroscopy. The results showed a hematite crystal form in the case of Fe2O3(2) and Fe2O3 samples, while the Fe2O3(1) sample showed a combination of hematite and synthetic mineral akaganeite. The highest photocatalytic efficiency was achieved in the presence of Fe2O3/TiO2/PVC, when 70.6% of MB was removed. In addition, the possible photo-cleaning and reuse of the mentioned photocatalyst was also examined. Based on the results, it can be seen that the activity did not decrease after five successive runs. Nanocomposites also exhibited mild antibacterial effects against the two tested Gram-positive bacteria (S. aureus and B. cereus)

Reusable Fe2O3/TiO2/PVC Photocatalysts for the Removal of Methylene Blue in the Presence of Simulated Solar Radiation

Currently, environmental pollution by various organic pollutants (e.g., organic dyes) is a serious, emerging global issue. The aqueous environment is highly exposed to the harmful effects of these organic compounds. Furthermore, the commonly applied conventional purification techniques are not sufficient enough. Heterogeneous photocatalysis and the photo-Fenton process are effective, low-cost and green alternatives for the removal of organic pollutants. In this study, different iron(III) oxide/titanium(IV) oxide/polyvinyl chloride (Fe2O3/TiO2/PVC) nanocomposites in tablet form were investigated in the photodegradation of methylene blue (MB) under simulated sunlight, and their possible antibacterial effects were examined. The newly synthesized nanocomposites were characterized by scanning electron microscope, X-ray diffraction, UV–Vis diffuse reflectance spectroscopy, and Raman spectroscopy. The results showed a hematite crystal form in the case of Fe2O3(2) and Fe2O3 samples, while the Fe2O3(1) sample showed a combination of hematite and synthetic mineral akaganeite. The highest photocatalytic efficiency was achieved in the presence of Fe2O3/TiO2/PVC, when 70.6% of MB was removed. In addition, the possible photo-cleaning and reuse of the mentioned photocatalyst was also examined. Based on the results, it can be seen that the activity did not decrease after five successive runs. Nanocomposites also exhibited mild antibacterial effects against the two tested Gram-positive bacteria (S. aureus and B. cereus)