Laccases for Soil Bioremediation

Bioremediation tool, by diminishing noxiousness or promoting pollutant mineralization to CO2 and water, is one of the most efficient, cost-effective, and eco-friendly approaches for the rehabilitation of polluted soils. Bioremediation process is mainly based on the ability of different enzymes or complex enzymes to act on various substrates. Laccases are ligninolytic enzymes, classified as benzenediol oxygen reductase (EC 1.10.3.2) and also known as multicopper oxidases. They are widely distributed in insects, plants, archaea, fungi, and bacteria. Industrially, laccases coming from fungi are the most commonly used; however, recently bacterial laccases have attracted attention because of their versatility, which includes higher thermostability, better tolerance to different concentrations of Cu2+, and higher resistance to changes regarding pH and halo and high chloride. The versatility of laccases allows its use on the soil to polymerize pollutants, and it also permits the bioaugmentation with immobilized laccases to degrade pollutants. Taking into account that laccase is one of the oldest enzymes ever described and it is relevant to the decomposition of xenobiotics, the present chapter will be dedicated to the exploration of laccase as an invaluable tool for soil bioremediation. We will review the main aspects related to the structure of laccases, substrates, and mechanisms of action. Additionally, we will also focus on two main topics: the production and the immobilization techniques to enhance the availability and stability of laccases. We highlighted some of the successful strategies employed to enhance laccase production, including the screening of new promising laccase, recombinant laccase production, as well as different immobilization strategies applied to increase the enzyme’s stability.