Trace metals as key controlling switches regulating the efficiencies of aerobic and anaerobic bioprocesses

The global demand for energy due to growing population is causing tremendous pressure on the depleting fossil fuel reserves. This along with the consequences of fossil fuel burning and associated environmental pollution has necessitated focused research on alternative sustainable options for energy generation and waste mitigation. Research on metal ions has mainly targeted the removal of heavy metals while, research on their beneficial impacts on the aerobic and anaerobic bioprocesses is restricted to few industrial applications. This review attempts to plug the aforesaid lacunae by giving a comprehensive insight into the impacts and critical roles of metals in enhancing/deterioration of bioprocess efficiencies. The aim of the review is to develop a mechanistic understanding about the essential role played by the metals such as iron, nickel, cobalt, molybdenum in enhancing the performance of aerobic and anaerobic processes by stimulating the relevant enzymes. It gives comprehensive discussion and analysis of the necessity and involvement of metals as driving force for shaping the performance of various stages of the anaerobic digestion pathway and also the aerobic phenomena like the stimulation of biofilm formation to granulation through critical effects on the underlying microbial community. The comprehensive understanding of trace metal supplementation as micronutrients and their interaction with metalloproteins can aid in designing strategies for hastening the bioprocesses.