Nanocellulase-assisted preparation technology: green and efficient nanocellulose production technology

Nanocellulase -assisted preparation technology: green and efficient nanocellulose production technology

Nano-cellulose, as a high-performance bio-based nanomaterial, has shown great application potential in composite materials, flexible electronics, biomedicine and other fields. However, traditional nanocellulose preparation methods (such as acid hydrolysis and mechanical methods) have problems such as high energy consumption and environmental pollution. As a green and efficient preparation process, enzyme-assisted method has attracted widespread attention in recent years. This article will conduct in-depth discussions on the principles, process flow, advantages and future development directions of nanocellulase-assisted methods.

The principle of enzyme-assisted method

Enzyme-assisted method uses cellulase (Cellulase) to biodegrade natural cellulose, selectively destroying the amorphous region of cellulose and retaining the crystalline region, thereby preparing nanocellulose. Cellulase is a complex enzyme that mainly includes the following three components:

Endoglucanase: Randomly cuts the β-1,4-glycosidic bonds inside the cellulose chain to produce short-chain cellulose.

Exoglucanase: Cut from the end of the cellulose chain in turn to release cellobiose.

β-Glucosidase: Hydrolyze cellobiose into glucose.

By regulating the composition and reaction conditions of the enzyme, efficient degradation of cellulose can be achieved and nanocellulose can be prepared.

The process flow of enzyme-assisted method

1. Raw material pretreatment

Raw material selection: Commonly used natural cellulose raw materials include wood, cotton, straw, hemp, etc.

Crushing and washing: Crush the raw materials into fine particles and wash them with deionized water to remove impurities and soluble ingredients.

Dry: The washed cellulose is dried at 60-80°C to a constant weight.

2. Enzymatic lysis reaction

Enzyme solution preparation: Dissolve cellulase in buffer solution and adjust the pH to 4.8-5.5 (optimal pH range).

Reaction conditions:

Mass ratio of enzyme to cellulose: 1:10 to 1:20.

Reaction temperature: 45-55°C (optimal temperature range).

Reaction time: 12-48 hours.

Stirring speed: 100-200 rpm to ensure uniform reaction.

Reaction process: The pretreated cellulose is added to the enzyme solution and the reaction is stirred under constant temperature. Enzymatic lysis destroys the amorphous region of cellulose and releases nanocellulose.

3. Reaction termination and purification

Enzyme inactivation: Enzymatic lysis reaction is terminated by heating (80-90°C, 10-15 minutes) or adjusting the pH to the non-optimal range.

Centrifugation: The nanocellulose suspension was isolated by centrifugation (10,000-15,000 rpm, 10-20 minutes).

Dialysis purification: The nanocellulose suspension was loaded into a dialysis bag, dialyzed with deionized water until the pH was close to neutral, and the residual enzyme and degradation products were removed.

4. Dispersion and drying

Ultrasonic dispersion: The purified nanocellulose suspension is sonicated (power 200-500 W, time 10-30 minutes) to ensure uniform dispersion of nanocellulose.

dry:

Freeze-drying: After freezing the nanocellulose suspension, the moisture is sublimated under vacuum to obtain fluffy nanocellulose powder.

Spray drying: The nanocellulose suspension is passed through a spray dryer and quickly dried to obtain nanocellulose powder.

Key parameters of enzyme-assisted method

The following are the key parameters and typical ranges for the preparation of nanocellulose by enzyme-assisted methods:

parameter	Typical range	Influence
Mass ratio of enzyme to cellulose	1:10 to 1:20	If the proportion is too high, it will increase the enzyme consumption, and if the proportion is too low, the enzyme is incomplete.
Reaction temperature	45-55°C	Too high temperature will lead to inactivation of the enzyme, and too low temperature will lead to slow reaction rate.
Reaction time	12-48 hours	If the time is too short, the enzymatic solution is incomplete, and the time is too long, it may lead to the destruction of the crystallization region.
pH value	4.8-5.5	Too high or too low pH will affect the activity of the enzyme.
Stirring speed	100-200 rpm	Ensure uniform reactions and avoid local overheating or incomplete reactions.
Centrifugal speed	10,000-15,000 rpm	If the speed is too low and the separation is not thorough, the speed is too high, it may destroy the nanocellulose structure.
Ultrasonic power	200-500 W	The power is too low and the dispersion is uneven, and too high power may destroy the nanocellulose structure.
Ultrasound time	10-30 minutes	If the time is too short and the dispersion is insufficient, the time is too long, it may lead to the degradation of nanocellulose.

Advantages of enzyme-assisted method

Green and environmental protection: The enzyme-assisted method uses biological enzymes as catalysts to avoid the use of chemicals such as strong acids and strong alkalis and reduce environmental pollution.

High efficiency and energy saving: The enzymatic reaction conditions are mild, the energy consumption is low, and it is suitable for large-scale production.

Excellent product performance: Nanocellulose prepared by enzyme-assisted method has high crystallinity, high mechanical strength and good dispersion.

Multifunctionality: By regulating the composition and reaction conditions of the enzyme, nanocellulose of different forms and properties can be prepared.

Challenges of enzyme-assisted method and future development direction

Although enzyme-assisted methods show great potential in nanocellulose preparation, there are still some challenges:

The cost of enzymes is higher: The production cost of cellulases is higher, limiting their large-scale application.

Long reaction time: Enzymatic reaction usually takes a long time, affecting production efficiency.

Enzyme stability: The activity of the enzyme is greatly affected by factors such as temperature and pH, and further optimization of reaction conditions is needed.

In the future, the development directions of enzyme-assisted methods include:

Genetic engineering transformation of enzymes: improve the activity and stability of cellulases through genetic engineering technology and reduce production costs.

Enzyme immobilization technology: immobilize the enzyme on the carrier, improve the reuse rate of enzyme and reduce production costs.

Compound enzyme system: Develop a complex enzyme system to improve the enzymatic lysis efficiency and shorten the reaction time.

Continuous production: Develop a continuous enzymatic process to improve production efficiency and reduce costs.

Conclusion

As a green and efficient nanocellulose preparation process, the enzyme-assisted method has broad application prospects. Through continuous optimization and innovation, enzyme-assisted methods are expected to play an important role in the large-scale production of nanocellulose, promoting their wide application in composite materials, flexible electronics, biomedicine and other fields. With the advancement of biotechnology and materials science, enzyme-assisted methods will provide more environmentally friendly and efficient solutions for the production of nanocellulose.

References

Klemm, D., et al. (2011). Nanocelluloses: A New Family of Nature-Based Materials. Angewandte Chemie International Edition, 50(24), 5438-5466.

Moon, RJ, et al. (2011). Cellulose Nanomaterials Review: Structure, Properties and Nanocomposites. Chemical Society Reviews, 40(7), 3941-3994.

Isogai, A. (2013). Wood Nanocelluloses: Fundamentals and Applications as New Bio-Based Nanomaterials. Journal of Wood Science, 59(6), 449-459.