###### Abstract  
Mushroom Ligninolytic enzymes are attractive biocatalysts that can degrade lignin through oxido-reduction. Lacase, lignin peroxidase, manganese peroxidase, and versatile peroxidase are the main enzymes that depolymerize highly complex lignin structures containing aromatic or aliphatic moieties and oxidize the subunits of monolignol associated with oxidizing agents. Among these enzymes, mushroom lacases are secreted glycoproteins, belonging to a polyphenol oxidase family, which have a powerful oxidizing capability that catalyzes the modification of lignin using synthetic or natural mediators by radical mechanisms via lignin bond cleavage. The high redox potential lacase within mediators can catalyze the oxidation of a wide range of substrates and the polymerization of lignin derivatives for value-added chemicals and materials. The chemoenzymatic process using mushroom lacases has been applied effectively for lignin utilization and the degradation of recalcitrant chemicals as an eco-friendly technology. Lacase-mediated grafting has also been employed to modify lignin and other polymers to obtain novel functional groups able to conjugate small and macro-biomolecules. In this review, the biochemical features of mushroom ligninolytic enzymes and their potential applications in catalytic reactions involving lignin and its derivatives to obtain value-added chemicals and novel materials in lignin valorization are discussed. l igininolytic enzyme; mushroom; lacase; lignin peroxidase; manganese peroxidase; versatile peroxidase; lignin valorization; lignin bioconversion; lacase-mediated grafting +
Footnote †: journal: Medical  
and chemical reactions, and the lysed monomers or oligomers can then be converted to renewable products through chemical or biological catalysts [1; 2; 3; 4]. Theoretically, the main three fractions (% dry wt), cellulose (30-50%), hemicellulose (15-34%), and lignin (9-32%), from renewable sources could be converted completely to fuels and chemicals within the concept of net-zero emissions technology [5]. Nevertheless, different physical or chemical pretreatment procedures are employed for various types of lignocellulosic biomass, which may influence the downstream process for the conversion efficiency and productivity of final products [5; 6]. Over recent decades, the process of the extraction of cellulose and hemicellulose linked to lignin from different types of biomass has been well-established to obtain fermentable sugars for the production of cellulosic biofuels or bio-building-block substances for chemical polymers [1; 2; 4]. Since cellulose and hemicellulose consist of simple or uniform monosaccharide subunits, these fractions can be extracted easily as monomeric or oligomeric sugars through pretreatment processes rather than lignin-containing complex heteropolymers within aromatic structures [6; 7; 8]. Most of the conventional pretreatments comprised chemical methods combined with physical processes to enhance the cellulose content per gram of biomass or to extract hemicellulose fractions [6; 7; 8; 9; 10; 11]. However, lignin fractions are released as byproducts of these pretreatment processes [7; 10; 12]. The high content lignin substances are then found in the wastewater generated by the pretreatment processes. Treatment of this wastewater accounted for approximately 20% of overall production costs [13]. The extracted lignin could be potentially utilizable for renewable chemicals to reduce non-utilized materials from biomass and overall production costs down for a sustainable green technology [14]. Lignin consists of aromatic heteropolymers with complex chemical linkages. The heteropolymeric structures contain hydroxyl, methoxyl, carbonyl, and carboxyl groups linked to aromatic or aliphatic moieties, with different molecular weights [15]. Lignin valorization is challenging due to the complexity of its structures compared with other cellulose and hemicellulose polymers [15; 16].