## 1 Introduction  
Biomass primarily of plant cell wall and age polysaccharides, including cellulose, hemicellulose, pectin and lignin, constitutes the major constituents of dietary fibre [1,2]. As an important dietary polymer nutrient, dietary fibre is utilized by various species of animals [2; 3]. Microbial degradation of these fibre components in the gastrointestinal tract is indispensable in maintaining healthy gut functions, gaining energy, aiding digestion of minerals and providing vitamins to the host [2; 3]. Lignin, representing a large group of aromatic polymers, and native cellulose of the quasi-crystalline structure in the lignocellulosic composite are mainly responsible for the recalcitrance of plant cell wall by limiting accessibility to biomass degrading microbial enzymes [4; 5; 6; 7; 8]. Microorganisms have evolved a multiplicity of enzymes to effectively degrade the composite structure of lignocellulosic-based biomass, including lacases and peroxididases, glycoside hydrolases such as cellulases and hemicellulases, polysaccharide lysates, lytic polysaccharide mono-oxygenases (LDMO) and the carbohydrate esterases to harvest metabolic energy ATP in adapting to their diverse environments [9; 10; 11; 12; 13; 14]. Thus, microbial biomass degrading cellulases are a group of important biocatalysts for biomass industrial applications. The enzymatic degradation of biomass polysaccharides is initiated by the cleavage of glycosidic bonds in the backbone. Thus, the major scientific-technological hurdle for effective utilization of lignocellulosic biomass is to develop efficacious industrial biomass-degrading biocatalysts for cost-effective degradation of lignocellulosic polymer into their constituent simple sugars such as glucose and pentoses, including xylose, mannose, galactose and arabinose, as illustrated in Figure 1. Lignocellulosic matrix is covered by a protective sheath locked by heterogenous polymers such as hemicelluloses, pectin and guar gum in cross-linkages with lignin. Among a variety of glycosidic bonds, \(\beta\)-1.4-glycosidic linkage is the most widely distributed bond in plant cell wall polysaccharides such as in cellulose and some hemicelluloses [1; 11; 15]. Collectively, these two group fibre components account for approximately 60% of plant cell wall materials [16; 17; 18], making \(\beta\)-1.4-glycosid bond cleavage one of the key biochemical reactions for biomass degradation [5; 12; 15]. As the most abundant biosynthetic polymer on the planet, native cellulose, referred to as cellulose I, has two distinct crystallite forms with 1\(\alpha\) being dominant in bacterial and algal celluloses and 1\(\beta\) being dominant in celluloses of higher plant origins [19]. It is believed that the two crystalline cellulose allomorphs of 1\(\alpha\) and 1\(\beta\) coexist with partially amorphous cellulose in most natural lignocellulosic of biomass materials; and an all-atom coarse-grained simulation model has been developed in describing the conversion process between the cellulose Ia and Ib allomorphs, characterizing the interface between the two crystalline forms of the allomorphs and determining their amorphous transition states under the room-temperature [20]. It has been estimated that the yearly biomass production of cellulose in the world is at about 1.5 trillion tons, making it an essentially inexhaustible resource for mankind [21]. By assuming effective pre-treatment and the use of highly efficacious cellulase enzymes and microbes capable of fermenting and processing hexose and pentose sugars in biorefineries, an integrated methodology of modelling assessment revealed that deployment of wheat straw could be economically feasible for producing liquid transportation fuel ethanol, biomaterial ethyl levulinate and electricity meanwhile gaining a positive environmental margin in terms of mitigating a significant amount of annual CO\({}_{2}\) emission [22; 23].