Bacterial laccases: promising biological green tools for industrial applications

Abstract

Multicopper oxidases (MCOs) are a pervasive family of enzymes that oxidize a wide range of phenolic and nonphenolic aromatic substrates, concomitantly with the reduction of dioxygen to water. MCOs are usually divided into two functional classes: metalloxidases and laccases. Given their broad substrate specificity and eco-friendliness (molecular oxygen from air as is used as the final electron acceptor and they only release water as byproduct), laccases are regarded as promising biological green tools for an array of applications. Among these laccases, those of bacterial origin have attracted research attention because of their notable advantages, including broad substrate spectrum, wide pH range, high thermostability, and tolerance to alkaline environments. This review aims to summarize the significant research efforts on the properties, mechanisms and structures, laccase-mediator systems, genetic engineering, immobilization, and biotechnological applications of the bacteria-source laccases and laccase-like enzymes, which principally include Bacillus laccases, actinomycetic laccases and some other species of bacterial laccases. In addition, these enzymes may offer tremendous potential for environmental and industrial applications.

Laccases: structure, function, and potential application in water bioremediation

“…The most significant biochemical properties of bacterial laccases are their stability under various conditions of pH, temperature, organic solvents, and salt concentrations [105]. Usually, bacterial laccases are highly stable at elevated temperatures, as seen in the B. subtilis laccase at 70 °C, with a thermal half-life (t 1/2 ) of 250 min, or the t 1/2 of 30 min at 80 °C of the Streptomyces viridochromeogenes laccase, compared with the 10 min t 1/2 of Cerrena unicolor fungal laccase at the same temperature [112–115].…”

Structural analysis and biochemical properties of laccase enzymes from two Pediococcus species

“…The purified recombinant protein showed a deep blue colour and exhibited a maximum peak at 600 nm in the UV-visible absorption spectrum (Fig. 2B), which corresponds to the characteristic T1 copper centre absorbance peak of the MCOs (Guan et al, 2018).…”

“…ABTS was a remarkably efficient mediator for 2,6-DMP oxidation at pH 4.0, and mediated oxidation of some biogenic amines (see below). We also investigated the oxidation of 2,6-DMP by both recombinant laccases using two other well-known laccase redox mediators, HBT and TEMPO, which act through distinct reaction mechanisms (Guan et al, 2018). HBT and TEMPO failed, as these two compounds were not substrates of Pp4816 and Pa5916 laccases at pH 4.0 or pH 7.5 (results not shown).…”

Inhibition in multicopper oxidases: a critical review

“…Since Solomon's influential review of multicopper oxidases and oxygenases in 1996, 1 there have been numerous review articles that cover MCOs. 9,[52][53][54][55][56][57][58] The dozens of reviews that were published from 2017 to the present include both general summaries 13,59,60 and more focused reviews that cover wastewater and soil remediation (including dye and pharmaceutical degradation); 38,39,41,[61][62][63][64][65][66][67][68][69][70][71][72][73][74][75] pulp, paper, lignin and wood processing (including lignin valorization); 67,68,[76][77][78][79][80] chemical synthesis; [80][81][82][83][84] polymer synthesis (including lignin formation); 79,[85][86][87][88]…”