Utilization of Benzoate and Phenol by Bacillus pumilus in Saline and Non-Saline Cultures

 Pollution by benzoate and phenol is currently a major global ecological challenge. Hence, utilization of benzoate and phenol by Bacillus pumilus in saline and non-saline cultures were tested in this work. Bacillus pumilus was challenged with benzoate and phenol at various salt concentrations (0 M, 1 M, 2 M, 3 M, 4 M, and control (positive control, which had bacteria but no benzoate or phenol, and in negative control, which had benzoate and phenol but no bacteria respectively). The isolate (obtained from stock culture in our laboratory and originally isolated from spent engine oil polluted soil), was identified using biochemical and molecular tests. The reaction setup included mineral salts medium (MSM), benzoate or phenol, and the bacterium. Bacillus pumilus inoculum was incubated at room temperature (25oC) in reaction tubes. Aseptically, 1.5 Eppendorf tubes were filled with 400μl of culture and centrifuged at 3,500 rpm for 10 minutes. 75μl supernatant was added to 1,425μl distilled water. Controls measured residual benzoate at 223 nm and phenol at 269nm. After 336 hours, reaction tubes were sacrificed after spectrophotometer readings. Readings began at hour 0 every two days. As the bacterium grew, residual benzoate decreased (from 0.779 nM to 0.417 nM for 0M NaCl, from 0.778 nM to 0.373 nM for 1M NaCl, from 0.754 nM to 0.583 nM in 2M NaCl, from 0.795 nM to 0.463 nM in 3M NaCl and from 0.803 nM to 0.368 nM in 4M NaCl). Bacillus pumilus used benzoate heavily. Increased salt concentrations decreased Bacillus pumilus phenol degradation (1M to 4M NaCl). Similar results were obtained for phenol. Bacillus pumilus can degrade phenol in halophilic and non-halophilic culture, but increasing the medium salt concentration inhibits cell growth. Bacillus pumilus degrades benzoate and phenol. Bacillus pumillus can remediate benzoate and phenol-polluted sites.