A comparative review towards potential of microbial cells for heavy metal removal with emphasis on biosorption and bioaccumulation

The threat of heavy metal pollution to environmental health is getting worldwide attention due to their persistence and non-biodegradable nature. Ineffectiveness of various physicochemical methods due to economical and technical constraints resulted in the search for a cost-effective and eco-friendly biological technique for heavy metal removal from the environment. The two effective biotic methods used are biosorption and bioaccumulation. A comparison between these two processes demonstrated that biosorption is a better heavy metal removal process than bioaccumulation. This is due to the intoxication of heavy metal by inhibiting their entry into the microbial cell. Genes and enzymes related to bioremoval process are also discussed. On comparing the removal rate, bacteria are surpassed by algae and fungi. The aim of this review is to understand the biotic processes and to compare their metal removal efficiency.