Optimization and Production of Exopolysaccharides (EPS) and Indole-3-Acetic Acid (IAA) Under Chromium by Halophilic Bacteria Oceanobacillus oncorhynchi W4

Abstract

The current study assessed the levels of exopolysaccharides (EPS) and indole-3-acetic acid (IAA) and the impacts of halophilic bacteria Oceanobacillus oncorhynchi W4 under Cr (VI). The effects of W4 were tested for its ability to remove Cr (VI) at several concentrations, the removal rate was 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 initial concentration of 50 mg/L (Cr (VI)). 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 (314.5 mg/L) was obtained under 96 h at pH 7.0, with 5% sucrose concentration. The strain Oceanobacillus oncorhynchi W4 was tested for its ability to create EPS at various concentrations of Cr (VI). After 96 h, 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 W4 was tested for its ability to secrete Indole-3 acetic acid. IAA secretion (control) without Cr (VI) achieved a maximum of 1.45 mg/ml at 120 h. At 200 mg/L Cr (VI) concentration, 1.65 mg/ml of IAA was also produced after 48 h. According to the findings, Oceanobacillus oncorhynchi W4 was a promising isolate in a stressful environment.

Keywords: Oceanobacillus oncorhynchi W4; Exopolysaccharide; Heavy metal; Indole -3 acetic acid.