Abstract
The global rise in urbanization and industrial activity has led to the production and incorporation of foreign contaminant molecules into ecosystems, distorting them and impacting human and animal health. Physical, chemical, and biological strategies have been adopted to eliminate these contaminants from water bodies under anthropogenic stress. Biotechnological processes involving microorganisms and enzymes have been used for this purpose; specifically, laccases, which are broad spectrum biocatalysts, have been used to degrade several compounds, such as those that can be found in the effluents from industries and hospitals. Laccases have shown high potential in the biotransformation of diverse pollutants using crude enzyme extracts or free enzymes. However, their application in bioremediation and water treatment at a large scale is limited by the complex composition and high salt concentration and pH values of contaminated media that affect protein stability, recovery and recycling. These issues are also associated with operational problems and the necessity of large-scale production of laccase. Hence, more knowledge on the molecular characteristics of water bodies is required to identify and develop new laccases that can be used under complex conditions and to develop novel strategies and processes to achieve their efficient application in treating contaminated water. Recently, stability, efficiency, separation and reuse issues have been overcome by the immobilization of enzymes and development of novel biocatalytic materials. This review provides recent information on laccases from different sources, their structures and biochemical properties, mechanisms of action, and application in the bioremediation and biotransformation of contaminant molecules in water. Moreover, we discuss a series of improvements that have been attempted for better organic solvent tolerance, thermo-tolerance, and operational stability of laccases, as per process requirements.
Highlights
Urbanization and industrialization have resulted in a serious contamination of water bodies, causing harmful effects to ecosystems
Laccases are widely expressed in nature; they can be obtained from various fungi, plants, bacteria, lichen, and insects (Fig. 2), with laccases from each species exhibiting particular catalytic characteristics and sequences [20,21,22]
It can be predicted that this large number of enzymes produced by different organisms could have a wide range of applications in water bioremediation (Fig. 2)
Summary
Urbanization and industrialization have resulted in a serious contamination of water bodies, causing harmful effects to ecosystems. Biotechnologists around the world are researching and developing innovative tools and nonpolluting processes to correct the effect of global pollution. This is challenging, owing to the quantity. Laccases, which belong to the enzyme family of multicopper oxidases (MCOs), are classified as benzenediol oxygen reductases (EC 1.10.3.2) and are known as urushiol oxidases and p-diphenol oxidases [15, 16] They are considered versatile enzymes capable of oxidizing a large number of phenolic and non-phenolic molecules due to their low substrate specificity, using oxygen as electron acceptor and generating water as a by-product [17,18,19]. We aim to describe laccases from different organisms, used in water bioremediation, their varying properties based on their origin, their biotechnological prospectives for pollutant degradation (fabric discoloration, herbicide degradation, and emerging pollutants transformation), and the different strategies that have been explored to increase their activity and application
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