Optimization and Production of Exopolysaccharides (EPS) and Indole-3-acetic acid (IAA) under chromium by halophilic bacteria Oceanobacillus oncorhynchi W4

Abstract

Abstract The current study assessed the levels of indole-3-acetic acid (IAA) and the impacts of halophilic bacteria Oceanobacillus oncorhynchi W4 exopolysaccharides (EPS) under Cr (VI) metal stress. The effects of W4 growth diminish with increasing concentrations of chromium. When the isolate Oceanobacillus oncorhynchi W4 was tested for its ability to remove Cr(VI) at several concentrations, the removal rate reached after 48 h at 58.4%, 53.3%, 49.2% and 43.1%. ) After 12–48 h, the maximum removal rate of 29–58% was found at an primary concentration of Cr(VI) of 50mg/L. The Box–Behnken design based on response surface methodology was utilized to optimize the EPS, including pH, sucrose concentration, and incubation period. The highest EPS yield (314.5mg/L) was obtained under 96 hours at pH 7.0, and 5% of sucrose concentration. The strain Oceanobacillus oncorhynchi W4 was tested for its ability to create EPS at various concentrations of Cr(VI). After 96 hours, it generated the maximum amount of EPS (216.3 mg/L) at a concentration of 50 mg/L. By using FT-IR spectrum measurements, it was confirmed that hexavalent chromium and EPS had surface chemical interactions. At various Cr(VI) concentrations, the isolate Oceanobacillus oncorhynchi W4 was tested for its ability to secrete IAA. IAA secretion of (control) without Cr(VI) achieved maximum of 1.45mg/ml at 120h. At 200mg/L Cr(VI) concentration, 1.65 mg/ml of IAA was also produced after 48h. According to the findings, Oceanobacillus oncorhynchi W4 was a promising isolate in the stressful environment.