Enzymes are already part of many manufacturing processes, but their industrial value is not simply that they can replace chemicals. Their real advantage is selectivity: a carefully chosen enzyme can modify a particular component of a complex material while leaving other components relatively intact. Two useful examples are pulp and paper manufacture, where cellulose-rich fibres must be processed without unnecessary damage, and leather production, where the collagen framework of animal hides must be preserved while unwanted substances are removed.

This article explains how enzymes work in these two industries, which microbial enzymes are important, and why operating conditions such as pH, temperature, reaction time and enzyme specificity determine whether treatment succeeds. It also separates established commercial applications from technologies that remain under development. The discussion is intended for microbiology, biochemistry, biotechnology and industrial microbiology students, as well as readers interested in cleaner manufacturing.

How enzymes contribute to industrial processing

An enzyme is a biological catalyst that accelerates a chemical reaction without being consumed in the overall process. Industrial enzyme formulations may contain a purified enzyme, an enzyme mixture, or a preparation produced by fermentation. Bacteria and filamentous fungi are important production hosts because they can be cultivated at scale and often secrete useful extracellular enzymes.

Enzymes used in fibre and hide processing must operate in challenging environments. A papermill may expose an enzyme to alkaline pH, elevated temperatures, dissolved chemicals and short residence times. A tannery may require a protease that removes non-collagenous proteins but does not appreciably digest the collagen fibres that give leather its strength. Consequently, enzyme selection is an engineering decision, not merely a matter of choosing an enzyme with high activity in a laboratory assay.

Part I. Applications in the pulp and paper industry

Paper is manufactured from plant fibres rich in cellulose, with varying amounts of hemicellulose, lignin, extractives and other components. In chemical pulping, much of the lignin is removed to separate usable fibres; additional bleaching may be required to increase brightness. Mechanical pulping retains more lignin, while paper recycling involves recovering fibres from previously printed or coated products. Different routes therefore create different opportunities for enzymes.

1. Xylanases in pulp bleaching

Xylanases catalyse the hydrolysis of xylan, an important hemicellulose in plant cell walls. During chemical pulping, residual xylan and lignin-associated material can make the remaining lignin less accessible to subsequent bleaching agents. Carefully controlled xylanase pretreatment modifies this hemicellulose fraction, often facilitating lignin extraction or bleaching and allowing mills to reduce the chemical requirement for a specified brightness target.

The preferred xylanase for many bleaching applications is active under the temperature and pH conditions of the process and has little or no unwanted cellulase activity. This matters because significant cellulose hydrolysis may reduce fibre strength or yield. However, there is no universally optimal treatment: effects vary with hardwood versus softwood pulp, pulping history, enzyme dosage and the bleaching sequence. Xylanase-assisted bleaching is an established industrial approach, but it should not be described as complete enzymatic replacement of chemical bleaching.

2. Lipases and esterases for pitch and stickies control

Wood contains extractives such as triglycerides and resin-associated substances that may accumulate as pitch deposits on machinery and paper. Certain lipases hydrolyse triglycerides, helping to change the properties of deposit-forming material and reduce operational problems. This application is particularly relevant to some mechanical-pulp and resin-rich systems.

A related challenge in recycled paper is stickies: adhesive contaminants from labels, tapes, coatings and other recovered materials. Selected esterases, lipases or enzyme combinations may help modify susceptible adhesive components. Their effectiveness depends on the chemistry of the contamination. Neither a lipase nor an esterase can be assumed to remove every deposit encountered in a mill.

3. Enzymatic deinking of recovered paper

Recycled fibres often retain printing ink and other surface contaminants. Deinking seeks to detach these materials from the fibres so they can be separated by flotation, washing or related operations. Cellulases and hemicellulases can modify the fibre surface or associated polysaccharides and help release ink particles. Enzyme-assisted approaches have been tested and developed alongside mechanical and chemical deinking methods.

The main trade-off is fibre preservation. Too much cellulase activity can shorten or weaken valuable cellulose fibres, even when ink release improves. Paper grade, ink formulation, treatment time and enzyme dose therefore matter. Enzymatic deinking is an active research and application area; a treatment successful on old newsprint should not automatically be assumed suitable for glossy magazines, office paper or packaging.

4. Cellulases in fibre modification and refining

Limited cellulase treatment can modify fibre surfaces and influence fibrillation, drainage, refining energy requirements and paper properties. The desired effect is controlled surface modification rather than extensive cellulose degradation. In practice, the balance among enzyme activity, fibre quality and operating conditions determines whether a formulation is useful.

5. Amylases for starch modification

Starch is widely used in papermaking, including as a strength additive and in surface-sizing formulations. Amylases hydrolyse starch and can be used to adjust its molecular size and viscosity for a specific application. This is a different function from xylanase-assisted bleaching: the enzyme acts on a processing additive rather than directly on residual hemicellulose in pulp.

6. Laccases and other oxidative enzymes

Laccases are multicopper oxidases that oxidize suitable phenolic compounds using molecular oxygen. Researchers have investigated laccase-based treatments, sometimes with mediator compounds, to modify lignin-derived structures, improve bleaching-related operations and influence deinking or fibre properties. Peroxidases and complementary enzymes are also being investigated. These methods are scientifically promising, but industrial implementation depends on reagent consumption, substrate accessibility, compatibility with process chemistry and cost. They should not be presented as universally established replacements for conventional bleaching.

A useful distinction for students: Biopulping generally refers to biological pretreatment of lignocellulosic material before pulping, often involving lignin-modifying fungi. Biobleaching refers to biological or enzyme-assisted operations that improve pulp bleaching. Enzymatic deinking targets the removal of ink from recovered paper. These terms describe different operations and should not be used interchangeably.

Part II. Applications in the leather industry

Raw hides and skins contain collagen, hair, fats, residual tissue and non-structural proteins. Leather manufacture converts this perishable biological material into a stable, usable product. Before tanning, several beamhouse operations prepare the hide by rehydrating it, removing unwanted material and opening the fibre structure. Proteases and lipases are particularly useful in these preparatory stages.

The overall sequence varies by tannery and material, but commonly includes preservation and soaking; liming and dehairing; fleshing and, where necessary, degreasing; deliming and bating; pickling; tanning; and subsequent finishing operations. The order of some stages and the need for particular treatments differ among processes. It is therefore misleading to treat soaking, dehairing, degreasing, bating and tanning as one universally fixed five-step method.

1. Soaking: rehydration and removal of soluble impurities

Hides may arrive fresh, chilled, wet-salted or dried. Soaking restores moisture and helps remove blood, dirt, salt and soluble residues. Water, surfactants and other process aids are selected according to the condition of the raw material. Appropriate proteases can assist in removing certain non-structural proteins, while lipases may help loosen fatty contaminants.

Enzymes used during soaking must be carefully controlled. Overly aggressive proteolysis can affect the grain or collagen structure; insufficient treatment may leave residues that interfere with later steps. The aim is effective cleaning and rehydration while preserving the structural proteins of the hide.

2. Dehairing: removing hair without damaging the hide

Conventional dehairing frequently uses lime and sulfide-containing chemicals to loosen or destroy hair. In hair-destroying processes, the hair is largely degraded; in hair-saving approaches, more intact hair may be recovered and separated from the processing liquor. This distinction matters because dissolved hair contributes organic matter to wastewater.

Proteases are investigated and used to assist dehairing by acting on proteinaceous material associated with hair follicles and surrounding tissues. Enzyme-assisted treatments can sometimes reduce sulfide requirements and facilitate hair recovery, but performance depends strongly on enzyme specificity. An enzyme that also attacks collagen or other important hide components can produce grain damage or weaken the leather. Complete replacement of conventional dehairing chemicals is not a universal industrial outcome.

Environmental benefits must be evaluated for the whole process. Reducing sulfide inputs or recovering hair can be advantageous, but numerical reductions in chemical oxygen demand (COD), biochemical oxygen demand (BOD), sulfide or water use vary across processes. Any percentage should be tied to a specific study and operating conditions rather than stated as an industry-wide guarantee.

3. Degreasing: lipase-assisted fat removal

Hides and skins differ substantially in fat content. In materials where fat interferes with subsequent processing, lipases catalyse the hydrolysis of triglycerides into glycerol and fatty acids, potentially making fat easier to remove when combined with appropriate washing or emulsifying systems. Degreasing may be particularly important for some sheepskins and pigskins.

Successful removal of excess fat can improve the uniformity of later dyeing and finishing. However, lipases do not guarantee complete removal of internal fat and do not, by themselves, make leather waterproof. The appropriate extent of degreasing depends on the intended leather product, raw material and subsequent processing steps.

4. Bating: selective removal of non-collagenous proteins

Bating is an enzyme treatment normally carried out after deliming and before tanning. Proteases remove selected non-collagenous proteins and help clean and relax the hide structure. When controlled well, bating can improve grain smoothness, softness and the penetration of subsequent processing agents.

This is a classic example of why enzyme selectivity matters: the process aims to remove undesirable protein material while retaining the collagen framework. Enzyme dose, pH, temperature and duration must be appropriate for the particular hide. Excessive treatment can lead to structural damage, while inadequate treatment may leave impurities and yield uneven results.

5. Tanning: what enzymes do and do not do

Tanning stabilizes collagen against microbial decomposition and other deterioration by forming interactions with tanning agents, including chromium-based or alternative organic and vegetable tanning systems. Proteases are not substitutes for these tanning agents simply because they are used earlier in hide preparation.

Research has examined enzyme-assisted pickling, improved penetration of tanning chemicals, and cleaner processing combinations. These approaches may be useful in carefully designed processes, but the primary role of proteases remains in preparing hides through operations such as soaking, dehairing and bating. Importantly, enzymes used for dehairing or bating must not be described as the chemicals that perform collagen tanning.

Terminology: Bating is the leather-processing term. It is not bathing. COD measures oxygen demand associated with chemically oxidizable substances in wastewater, whereas BOD measures oxygen consumed during biological degradation under defined test conditions. They are related but not interchangeable.

A comparison of enzymes and their industrial roles

Environmental benefits–and why they must be measured

The environmental rationale for enzyme-assisted manufacturing is straightforward: a selective biocatalyst may lower chemical inputs, energy consumption or wastewater burden while maintaining product quality. Nevertheless, “enzyme-based” is not synonymous with “pollution-free.” Enzyme manufacture, process water, electricity, formulation additives and downstream effluent treatment also have environmental footprints.

To compare a conventional and an enzyme-assisted process fairly, investigators should report the same functional output—such as a defined paper brightness and strength or a specified leather quality—and examine chemical use, water and energy demand, yield, wastewater characteristics and cost. Pilot studies and laboratory successes are valuable, but they do not automatically predict performance at commercial scale.

Current research and future directions

Recent work increasingly focuses on tailored enzyme preparations rather than treating each enzyme in isolation. In pulp processing, researchers study how xylanases, laccases, esterases and other activities may complement one another; in recycling, the challenge is effective contaminant release with minimal fibre deterioration. Work on enzyme thermostability, alkaline tolerance and dosage control aims to improve compatibility with industrial equipment and operating conditions.

In leather processing, attention has turned to selective proteases, lower-sulfide dehairing, carefully optimized bating and enzyme-assisted combinations of preparatory treatments. Protein engineering, recombinant production and immobilization are being investigated to improve performance, reuse or stability. A 2024 study of a Bacillus halodurans protease illustrates the continuing evaluation of microbial enzyme preparations for hide processing; such studies are evidence of technological development, not proof that a new process has been universally adopted.

For microbiology and biotechnology students, these developments make industrial enzymology a useful meeting point between microbial cultivation, enzyme kinetics, protein engineering, materials science and environmental assessment. Understanding the target substrate is only the beginning; the decisive question is whether an enzyme offers a controlled and economically practical improvement within a real manufacturing process.

Conclusion

Xylanases, lipases, cellulases, esterases, amylases and oxidative enzymes have roles in pulp and paper production that range from established process aids to emerging research applications. In leather production, proteases and lipases are especially relevant to preparing hides through soaking, dehairing, degreasing and bating. Across both industries, successful applications rely on selecting an enzyme for a specific substrate and controlling its activity so that valuable fibres or collagen are preserved.

The long-term promise of industrial enzymes lies not in replacing every chemical step, but in making selected operations more efficient, more controllable and potentially less resource-intensive. Real environmental gains must be demonstrated for the complete process rather than inferred from the use of a biological catalyst alone.

References and further reading

Walia, A., Guleria, S., Mehta, P., Chauhan, A., & Parkash, J. (2017). Microbial xylanases and their industrial application in pulp and paper biobleaching: A review. 3 Biotech, 7, Article 11. https://doi.org/10.1007/s13205-016-0584-6

Immerzeel, P., & Fiskari, J. (2023). Synergism of enzymes in chemical pulp bleaching from an industrial point of view: A critical review. The Canadian Journal of Chemical Engineering, 101(1), 312–321. https://doi.org/10.1002/cjce.24374

Saxena, A., & Chauhan, P. S. (2017). Role of various enzymes for deinking paper: A review. Critical Reviews in Biotechnology, 37(5), 598–612. 

https://doi.org/10.1080/07388551.2016.1207594

Hasan, M. J., Haque, P., & Rahman, M. M. (2022). Protease enzyme based cleaner leather processing: A review. Journal of Cleaner Production, 365, Article 132826. https://doi.org/10.1016/j.jclepro.2022.132826

Sujitha, P., Kavitha, S., Shakilanishi, S., Chandra Babu, N. K., & Shanthi, C. (2018). Enzymatic dehairing: A comprehensive review on the mechanistic aspects with emphasis on enzyme specificity. International Journal of Biological Macromolecules, 118, 168–179. https://doi.org/10.1016/j.ijbiomac.2018.06.081

Biškauskaitė, R., Lee, W.-C., & Valeika, V. (2024). Crude proteolytic enzyme from Bacillus halodurans BCRC 910501 and its application in leather processing. Heliyon, 10(16), Article e35842. https://doi.org/10.1016/j.heliyon.2024.e35842

Biškauskaitė, R., Valeikienė, V., & Valeika, V. (2021). Enzymes for leather processing: Effect on pickling and chroming. Materials, 14(6), Article 1480. https://doi.org/10.3390/ma14061480