RSM for optimization of mercury bioremediation by Vibrio

What is it about?

Three bacterial species of PG01, PG02 and PG03 were isolated from coastal sediments of Bushehr (Iran) as mercury-resistant bacteria. According to 16S ribosomal DNA gene sequence, the strains were identified as Vibrio natriegens, V. parahaemolyticus and Oceanimonas baumannii, respectively. Minimum inhibitory concentration test in the presence of HgCl2 revealed that the strain PG02 was the most resistant one, which tolerated up to 45 mg L-1 Hg2+. Tracing the growth curves for the PG02 showed that when it is initially exposed to 5 mg L-1 Hg2+ in the medium, only 10% of its natural growth is reduced, while it simultaneously succeeds to remove 90% of mercury. However, initially 10 mg L-1 Hg2+ in the medium led to 30% growth inhibition and 80% mercury removal. According to a linear relationship between the growth inhibition percentage and the initial mercury concentrations, the median effective concentration was calculated as 21.84 mg L-1 for PG02. Central composite design under response surface methodology well proposed a model with high values of R2 = 0.999 and adjusted R2 = 0.998 which predicted the maximum mercury removal of 89.47% by PG02 under optimum pH of 7.2, temperature of 37.5 °C and the initial mercury concentration of 5 mg L-1.

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