Cadmium resisting bacteria in Alexandria Eastern Harbor (Egypt) and optimization of cadmium bioaccumulation by Vibrio harveyi

Abstract

Cadmium resisting bacteria (CRB) were present in all water and sediments (samples) collected from Alexandria Eastern Harbor, Egypt. The occurrences of CRB in sediments samples were higher than in water samples and reached up to 77.22% of total counts. Five isolates were selected to be the most resistant to cadmium with minimal inhibitory concentration of 60 ppm. The most potent isolate that accumulates a maximum Cd²⁺ concentration of 23.3 mg Cd²⁺/ g dry cells was identified as Vibrio harveyi. Medium components affecting metal removal by V. harveyi were explored based on the application of Plackett-Burman design. The growth of V. harveyi in the optimized culture conditions, recorded cadmium biosorption of 1.52 fold increase. Immobilized living cells of V. harveyi on hazelnut shells increased the uptake of cadmium to 49.35 mg Cd²⁺/g dry cells and removal efficiency up to 84%. Transmission electron microscope study confirmed the accumulation of Cd²⁺ by V. harveyi cells.

Key words: Cadmium resisting bacteria, Vibrio harveyi, bioaccumulation, Plackett-Burman design.