Bioremoval of cadmium using a dual-chambered fluidized bed bioreactor: a biofilm-based approach

Cadmium is one of the toxic heavy metals which tend to accumulate in the biome posing threat to the living system. The present study investigated the cadmium removal efficiency by effective cadmium-resistant isolate in a novel dual-chambered horizontal continuous-flow bioreactor. Cadmium-resistant bacterial isolates were obtained from sewage effluent samples and were tested for their maximum tolerable concentration. The isolate VITKKAJ1 was found to be highly resistant to cadmium and exhibited high degree of biofilm formation. The capability of VITKKAJ1 in producing short-chain quorum-sensing molecules (acyl-homoserine lactone) was significantly correlated with the increased production of exopolysaccharides. Substrates such as gravels and alginate beads were packed in the perforated compartments of the bioreactor with a bed height of 15 cm for the adsorption of cadmium. The percentage removal of cadmium with and without biofilm (substrates) was 90.56 and 70.7%, respectively. The phylogenetic analysis based on 16S rRNA sequencing indicated the isolate to be a representative of Aeromonas diversa (Acc. No. KU560509).