Laccase grafted membranes for advanced water filtration systems: a green approach to water purification technology

Purpose: Conventional wastewater treatment technologies are not good enough to completely remove all endocrine disrupting compounds (EDCs) from the water. Membrane separation systems have emerged as an attractive alternative to conventional clarification processes for waste and drinking water. Coupling of a membrane separation process with an enzymatic reaction has opened up new avenues to further enhance the quality of water. This review article deliberates the feasibility of implementing enzymatic membrane reactors has been deliberated.

Materials and methods: A comprehensive study of conventional water treatment technologies was carried out and their shortcomings were pointed out. Research findings from the leading groups working on enzyme grafted membrane based water purification were summarized. This review also comprehends the patent documents pertinent to the technology of enzyme grafted membranes for water purification.

Results: Immobilization of an enzyme on a membrane improves the performance of membrane filtration, and processes for the treatment of polluted water. Research has started exploring the potential for laccase enzymes because it can catalyze the oxidation of a wide range of substrates, structurally comparable to EDCs, by a radical-catalyzed reaction mechanism, with corresponding reduction of oxygen to water in an electron transfer process. Further, in the presence of certain mediators, the substrate range of laccases can be further enhanced to non-aromatic substrates.

Conclusions: Removal of EDCs by laccase cross-linked enzyme aggregates in fixed-bed reactors or fluidized-bed reactors and laccase immobilized ultrafiltration (LIUF) membranes are proving their worth in water purification technology. The major operational issues with the use of LIUF membranes are enzyme instability in real wastewater and membrane fouling. In view of the above-stated characteristics, laccases are considered as the most promising enzyme for a greener and less expensive water purification technology.