# Lacase in Biorefinery of Lignocellulosic Biomass
###### 1 Introduction  
Liginocellular biomasses contain approximately 40-50% cellulose, 20-30% hemicellulose, and 20-30% lignin, as well as other minor components, such as ash and extractives [1]. Cellulose is a linear polymer of glucose molecules that are interconnected by \(\beta\)-1.4-glycosidic bonds. Hemicellulose is a heteropolymer composed of different sugar units that vary depending on the source of the biomass [2]. Lignin is a highly branched and cross-linked polymer that provides mechanical strength and protection against biotic and abiotic stresses. Lignin is a major component of plant biomasses, comprising up to 30% of the dry weight of woody plants. It plays an important role in providing rigidity and structural support to the cell walls, as well as protecting the plant from pests and pathogens. However, lignin is also responsible for the recalcitrance of plant biomasses, which makes it difficult to break down into its constituent parts [3]. Thus, the enzymatic breakdown of biomasses, as well as lignin, is a tedious and slow process, as nature has created themto provide resistance to the erected plants with a microbial attack. This has been a major challenge in the development of biofuels and other applications that require the use of plant biomasses as a feedstock. The conversion of plant biomasses into useful products via biorefinery has been the subject of intensive research in recent years [4]. Enzymatic conversion of biomasses into their monomeric components has been regarded as the most sustainable way. One of the main challenges in biomass conversion is the recalcitrance of lignin, which makes it difficult to break down into its constituent sugars. Laccase has been shown to play an important role in the conversion of lignin to its constituent parts. Additionally, lignin peroxidase, manganese peroxidase, and versatile peroxidase are known to act on lignin in synergy [5]. These enzymes are usually produced along with lactose by fungi, such as _Phanerochaete chrysosporium_, which enables the fungi to degrade lignin completely. The action and mechanism of each of these enzymes have been discussed by [PERSON] et al., 2022 [1]. Laccase is a type of enzyme that is widely distributed in nature, being produced particularly by fungi and bacteria. It catalyzes the oxidation of a wide range of substrates, including phenols, polyphenols, and aromatic amines [6; 7; 8]. Laccase is classified as an oxidoreductase enzyme because of its catalytic property allowing it to transfer the electrons from a substrate to an oxidant. It has been shown to be an efficient catalyst for the degradation of lignin [9]. This makes it an attractive target for the development of new technologies for the conversion of plant biomasses into useful products.  
Laccase acts by oxidizing lignin, which breaks it down into smaller molecules that can be more easily degraded by other enzymes. Laccase has also been shown to play a role in the conversion of other components of plant biomasses, including cellulose and hemicellulose [10]. In recent years, there has been a growing interest in using laccase-based technologies to break down lignin and other components of plant biomass [11]. This article will provide insight into the significance and contribution of laccase in biorefinery. Biomasses need to be pretreated first to undergo enzymatic treatment for any other biorefinery process. Biological pretreatment of biomasses by laccase is considered the most sustainable one. Laccase production via different modes of bioprocesses has been presented. This is a hot subject, as lignin valorization is much needed for an economically efficient biorefinery process of lignocellulosic biomasses. Laccase plays an extremely important role in this area.