Biodegradation and biological treatments of cellulose, hemicellulose, and lignin: an overview Cellulose, lignocellulose, and lignin are major sources of plant biomass, essential for the carbon cycle. These polymers are degraded by various microorganisms, which produce enzymes that work synergistically. Future technologies using lignocellulolytic enzymes or microorganisms could lead to environmentally friendly processes. This review discusses recent advances in biological treatments that convert these biopolymers into alternative fuels. It also outlines biotechnological innovations in natural delignification applied to pulp and paper manufacturing. Lignocellulose, the main component of biomass, consists of cellulose, hemicellulose, and lignin, which are strongly intermeshed. Many fungi and bacteria can break down these macromolecules using hydrolytic or oxidative enzymes. Molecular genetics of these degradation systems advanced significantly in the 1990s, with most enzymes cloned, sequenced, and expressed in various hosts. The structure, genomic organization, and regulation of these genes are well understood, though this review does not summarize these findings. Lignocellulose materials derive from wood, grass, agricultural residues, forestry wastes, and municipal solid wastes. Biological methods for lignocellulose recycling, based on enzyme degradation, have been proposed. Composting and using it for ethanol production are economically feasible. Using lignocellulose enzymes in pulp and paper manufacturing stages, such as biopulping, biobleaching, and wastewater treatment, saves energy and reduces pollutants. Pretreatment of agricultural wastes with ligninolytic fungi enables their use in paper manufacturing. Microorganisms or their enzymes can also enhance de-inking of recycled fibers and release toners from office waste. Cellulose is the major component of lignocellulose, making up about 45% of dry wood weight. It is a linear polymer of D-glucose linked by β-1,4 glycosidic bonds. Hemicellulose, a complex carbohydrate, makes up 25–30% of wood dry weight. It consists of various sugars linked by β-1,4 and occasionally β-1,3 glycosidic bonds. Lignin is an aromatic polymer synthesized from phenylpropanoid precursors. The structure of the wood wall is complex, with cellulose, hemicellulose, and lignin arranged in different layers. Cellulose can exist in crystalline or amorphous forms, with amorphous cellulose more susceptible to enzymatic degradation. Hemicellulose and lignin cover microfibrils, which are formed by elemental fibrils. The orientation of microfibrils varies in different wall levels.Biodegradation and biological treatments of cellulose, hemicellulose, and lignin: an overview Cellulose, lignocellulose, and lignin are major sources of plant biomass, essential for the carbon cycle. These polymers are degraded by various microorganisms, which produce enzymes that work synergistically. Future technologies using lignocellulolytic enzymes or microorganisms could lead to environmentally friendly processes. This review discusses recent advances in biological treatments that convert these biopolymers into alternative fuels. It also outlines biotechnological innovations in natural delignification applied to pulp and paper manufacturing. Lignocellulose, the main component of biomass, consists of cellulose, hemicellulose, and lignin, which are strongly intermeshed. Many fungi and bacteria can break down these macromolecules using hydrolytic or oxidative enzymes. Molecular genetics of these degradation systems advanced significantly in the 1990s, with most enzymes cloned, sequenced, and expressed in various hosts. The structure, genomic organization, and regulation of these genes are well understood, though this review does not summarize these findings. Lignocellulose materials derive from wood, grass, agricultural residues, forestry wastes, and municipal solid wastes. Biological methods for lignocellulose recycling, based on enzyme degradation, have been proposed. Composting and using it for ethanol production are economically feasible. Using lignocellulose enzymes in pulp and paper manufacturing stages, such as biopulping, biobleaching, and wastewater treatment, saves energy and reduces pollutants. Pretreatment of agricultural wastes with ligninolytic fungi enables their use in paper manufacturing. Microorganisms or their enzymes can also enhance de-inking of recycled fibers and release toners from office waste. Cellulose is the major component of lignocellulose, making up about 45% of dry wood weight. It is a linear polymer of D-glucose linked by β-1,4 glycosidic bonds. Hemicellulose, a complex carbohydrate, makes up 25–30% of wood dry weight. It consists of various sugars linked by β-1,4 and occasionally β-1,3 glycosidic bonds. Lignin is an aromatic polymer synthesized from phenylpropanoid precursors. The structure of the wood wall is complex, with cellulose, hemicellulose, and lignin arranged in different layers. Cellulose can exist in crystalline or amorphous forms, with amorphous cellulose more susceptible to enzymatic degradation. Hemicellulose and lignin cover microfibrils, which are formed by elemental fibrils. The orientation of microfibrils varies in different wall levels.