Cellulases

Cellulases are enzymes that hydrolyze cellulose, one of the most abundant organic polymers on the planet. Cellulose is a structural polysaccharide composed of long chains of β-1,4-linked glucose units. Cellulases break down cellulose into its constituent sugars, primarily glucose, which can be used for energy in organisms or for other industrial purposes. Cellulases are widely used in the biofuel, textile, food and paper industries.

Creative Enzymes offers a comprehensive range of premium cellulases sourced from diverse origins, including native and recombinant, as well as single and enzyme blends, catering to diverse applications.

Fig. 1: Structure of endo/exocellulase E4 from Thermomonospora fusca. PDB: 1JS4.

Functions of Cellulases

Cellulases are enzymes responsible for breaking down cellulose into simpler sugars, typically glucose. Cellulose is the primary component of plant cell walls and is highly resistant to degradation due to its crystalline structure and insolubility in water. Without cellulases, the breakdown of cellulose would be a slow process, impeding the carbon cycle and delaying nutrient turnover in ecosystems. Cellulases facilitate the conversion of cellulose into glucose by breaking down its complex structure, which can then be used in the metabolic pathways of microorganisms and other organisms that depend on it for energy. This enzymatic degradation of cellulose is vital to natural ecosystems, particularly in the decomposition of plant material, and is also of great importance in various industries that use plant biomass as a raw material.

Mechanism of Cellulase Action

The mechanism of action of cellulases involves the hydrolysis of the β-1,4-glycosidic linkages present in cellulose. However, cellulose degradation is not a straightforward process due to the complex and heterogeneous structure of the substrate. To overcome this, cellulases work in synergy with a number of enzyme components to perform efficient cellulose degradation. These enzymes act on different parts of the cellulose structure, allowing for more complete degradation of the polymer.

Fig. 2: Cellulose polymer containing glucose monomers linked by β-1,4 glycosidic bonds.

Modes of Action

Cellulases generally act through three main modes of action:

• Endoglucanases (EGs): These enzymes cleave internal β-1,4 glycosidic bonds within the cellulose chain. They create random breaks, generating new chain ends that serve as substrates for other cellulase enzymes. By breaking the internal bonds, endoglucanases reduce the degree of polymerization of cellulose, exposing more sites for enzymatic activity.
• Exoglucanases (CBHs): Also known as cellobiohydrolases, these enzymes cleave cellulose at the chain ends, releasing cellobiose (a disaccharide of glucose units) as the major product. Exoglucanases primarily target crystalline cellulose, a highly ordered and structured form of cellulose, and work by progressively removing cellobiose from the chain ends.
• β-glucosidases: These enzymes hydrolyze cellobiose and other short oligosaccharides into individual glucose units. This step is critical to sustain the enzymatic process because accumulated cellobiose inhibits upstream cellulase activity. This ensures complete hydrolysis of cellulose to glucose.

Synergistic Action

Efficient cellulose degradation requires the synergistic action of endoglucanases, exoglucanases and β-glucosidases. Endoglucanases first break down the cellulose structure to create new chain ends, followed by exoglucanases acting on these ends to produce cellobiose. β-Glucosidases then convert cellobiose to glucose, which can be used in various metabolic or industrial processes.

Cellulase activity is also affected by other factors such as pH, temperature, substrate accessibility, and the presence of inhibitors. The cellulase complex, often secreted by microorganisms, facilitates the binding of the enzymes to the cellulose substrate, thereby increasing the overall degradation efficiency.

Fig. 3: The three types of reaction catalyzed by cellulases: 1. Breakage of the noncovalent interactions present in the amorphous structure of cellulose (endocellulase) 2. Hydrolysis of chain ends to break the polymer into smaller sugars (exocellulase) 3. Hydrolysis of disaccharides and tetrasaccharides into glucose (beta-glucosidase) (Gomez del Pulgar and Saadeddin, 2014).

Sources of Cellulases

Cellulases are produced by a wide variety of organisms, including microorganisms, plants and animals, although microbial sources are by far the most important for both natural ecosystems and industrial applications.

Microbial Sources

Microorganisms such as fungi, bacteria and actinomycetes are the primary producers of cellulases. These organisms play a crucial role in the breakdown of cellulose in nature and are also used for the industrial production of cellulases.

• Fungi: Filamentous fungi, particularly those of the genera Trichoderma, Aspergillus, and Penicillium, are among the most prolific producers of cellulases. Fungal cellulases are secreted extracellularly and are capable of degrading both amorphous and crystalline cellulose.
• Bacteria: Certain bacteria, such as Bacillus subtilis, Clostridium thermocellum, and Cellulomonas fimi, are capable of producing cellulases. Bacterial cellulases often have high activity at extreme temperatures and pH levels, making them suitable for use in harsh industrial processes.

Plant Sources

While plants do not produce cellulases in quantities suitable for industrial applications, certain plants produce cellulolytic enzymes during certain stages of growth or in response to injury. For example, cellulase activity is involved in fruit ripening, where it helps soften plant cell walls by breaking down cellulose.

Animal Sources

Some animals, particularly herbivorous insects and ruminants, have symbiotic relationships with cellulase-producing microorganisms in their digestive systems. Termites, for example, rely on cellulase-producing protozoa and bacteria in their guts to digest wood. Similarly, ruminants such as cows and sheep harbor cellulolytic bacteria in their rumen to break down plant fibers into digestible sugars.

Types of Cellulases

Thermophilic and Acidophilic Cellulases

Some cellulases are classified based on their ability to function under extreme conditions, such as high temperature or low pH. Thermophilic cellulases function optimally at high temperatures, often above 70 °C. These cellulases are particularly valuable in industrial processes that require high-temperature reactions, as they offer greater stability and efficiency compared to their mesophilic counterparts. Examples are thermostable cellulases from Dictyoglomus turgidum, and from Clostridium thermocellum.

Acidophilic cellulases operate optimally under acidic conditions and are used in processes such as the hydrolysis of lignocellulosic biomass where acidic conditions prevail. Our offerings in this category include acid cellulase for textile, highly concentrated acid cellulase (industrial grade), and acid cellulase for bio-polishing.

Applications of Cellulases

The wide range of cellulase applications spans several industries, from bioenergy production to food processing and textile manufacturing. These applications are primarily driven by the enzyme's ability to break down cellulose into simpler sugars, which can then be used in various processes.

Quickly browse our product offerings by application below:

Food and Beverage Industry

In the food and beverage industry, cellulases are used to improve the extraction of juices from fruits and vegetables, to clarify fruit juices, and to increase the digestibility of animal feeds. They are also used in brewing to break down polysaccharides in barley, improve filtration, and increase the release of fermentable sugars. Another important application is barking (cellulase for baking). Cellulases, which break down cellulose in plant cell walls, improve water absorption and soften the texture of baked goods. Cellulases also help increase the volume and shelf life of bread by changing the structure of the dough.

Textile Industry

In the textile industry, cellulases are used for biopolishing (acid cellulase for bio-polishing) and fabric softening. Biopolishing involves the removal of small fibers or lint from the surface of fabrics, resulting in a cleaner, smoother finish and improved appearance (neutral cellulase for fabric). Cellulases are also used in the stonewashing process for denim garments, where they help create a worn look without the need for abrasive stones, reducing fabric damage and environmental impact (neutral cellulase for jeans).

Detergent

In laundry detergents, cellulase is used to improve fabric cleaning and care (alkaline cellulase for detergent). It works by breaking down small, damaged cellulose fibers on the fabric surface, reducing pilling and restoring smoothness, giving garments a fresher look. This enzymatic action also helps release trapped dirt and stains from these fibers, improving stain removal and enhancing fabric appearance. In addition, cellulase enables effective cleaning at lower temperatures, saving energy and making the washing process more environmentally friendly.

Pulp and Paper Industry

Cellulases are used in the pulp and paper industry to improve pulp properties and reduce the need for mechanical processing. They help to modify fibers, reduce the viscosity of pulps, and improve paper quality. Enzymatic treatments with cellulases can also reduce the use of harsh chemicals in bleaching processes, making the production process more environmentally friendly.

Biofuels

One of the most important applications of cellulases is the production of biofuels, particularly cellulosic ethanol. Cellulosic ethanol is produced by fermenting glucose derived from lignocellulosic biomass (plant material containing cellulose, hemicellulose, and lignin). Cellulases play a key role in hydrolyzing the cellulose in the biomass into fermentable sugars, which are then fermented by microorganisms into ethanol. This technology provides a renewable and sustainable energy source that reduces dependence on fossil fuels and lowers carbon emissions.

Waste Management

Cellulases have promising applications in waste management and environmental sustainability. They can be used in the bioconversion of agricultural waste, municipal solid waste, and other lignocellulosic materials into valuable products such as biofuels, bioplastics, and other chemicals. Cellulase-mediated processes provide a sustainable method of waste recycling by converting cellulosic waste into bioenergy and other useful products.

Pharmaceutical Industry

Cellulases are valuable in the pharmaceutical industry for improving drug formulation and delivery. They modify cellulose-based excipients in tablets, improving controlled drug release and increasing bioavailability of active ingredients. In addition, cellulases enhance the extraction of bioactive compounds from plant materials used in herbal medicines, thereby increasing their efficacy. They are also being explored in the development of biodegradable drug delivery systems, offering a more sustainable approach to pharmaceutical manufacturing.

Fig. 4: Applications of cellulases (Ranjan et al., 2023).

Advantages of Our Cellulases

Our cellulases offer distinct benefits, making them versatile across industries.

• Wide Range of Enzymes from Fungi and Bacteria: We offer both fungal and bacterial cellulases, providing options to meet different industrial needs. Fungal cellulases, known for their high activity, are ideal for biofuel production and paper processing, while bacterial cellulases excel in high temperature and extreme pH environments such as industrial fermentation and waste management. This broad selection enables flexible, customized solutions.
• Different Purity Levels: Our cellulases are available in various degrees of purity to suit specific applications. Crude cellulases are cost-effective for large-scale processes such as bioethanol production, while highly purified cellulases are essential for research and pharmaceutical applications that require precision and minimal impurities. This flexibility ensures cost and performance optimization.
• Native and Recombinant Forms Available: We offer both native and recombinant cellulases. Native cellulases are ideal for natural processes, while recombinant enzymes offer improved stability, activity and resistance to harsh industrial conditions. This versatility allows for better customization and consistency across different applications.

In conclusion, cellulases are essential enzymes of great ecological, industrial and economic importance. Their ability to break down cellulose into fermentable sugars has opened up numerous applications, from biofuel production to waste management and the food industry. The synergistic action of endoglucanases, exoglucanases and β-glucosidases is the key to efficient cellulose degradation and their properties can be optimized for different industrial needs. The versatility of cellulases, combined with their diverse sources, especially from microorganisms, makes them indispensable tools for numerous biotechnological applications.

Creative Enzymes offers cellulases characterized by diversity, tailored purity levels and availability in native or recombinant forms, making them a reliable choice in industries ranging from biofuels, textile, pulp and paper to food and beverage, and waste management. For inquiries and questions, please contact us today!